By Bob Goemans
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The 'LIVING' Marine Aquarium Manual

Basic and Advanced Husbandry for the 'Modern' Marine Aquarium

by Bob Goemans

Chapter 17 – Other Invertebrate Selection


Lets continue in this chapter with other invertebrate animals, e.g., crustaceans, clams, seastars, snails, crabs, and sponges to name just some, as there are a great variety of those of interest. The best way to do this in my opinion is to divide them into those falling within their proper classifications/taxonomy. I'll try to keep it simple and use only the Phylum name and those families of interest within it. Lets begin with those in the Phylum Arthropoda, which include barnacles, shrimp, clawed lobsters, hermit crabs, porcelain crabs, and true crabs.

(Please keep in mind all underlined word(s) are linkable files – just click on them and be taken to its content/photo. Also, all shown photos are clickable, which often allows a larger file to be seen.)

Phylum Arthropoda


These are mentioned here in this section because they are distantly related to crabs and lobsters and are sometimes found attached to live rock, corals, and other invertebrates. Barnacles, the only sedentary crustaceans, live in shells of fused plates permanently fastened to any hard substrate whether metal, wood, stone, turtle backs, or whale skin.

They have two larval stages with the first called the nauplius. It is part of the plankton, which is governed by the wind, waves, currents, and tides while it feeds and molts. This only takes about two weeks, then the second stage is reached at which time the nauplius metamorphoses into a non-feeding, more strongly swimming cyprid larva. They in turn try to find a suitable place to settle down where environment suits them. If they do, they grasp onto the surface with their short antennae and undergo a metamorphosis by rotating forwards and over so that the swimming legs point upwards. The carapace of the larva then splits a number of times depending on the species and forms plates seen as shells. If a suitable resting place is not found, the larvae die.

They do well in rough water, and require very good water circulation. Barnacles feed by beating their feather-like legs, called cirri, which in turn draw plankton from the passing water. Probably one of the more interesting genera for aquarists is Lepas and possibly the volcano shaped barnacles that encrust rocks in intertidal zones, such as those in the Family Tetraclitidae. However, they are extremely difficult to maintain, and are probably better left in the wild unless you're willing to provide the environment needed

Gooseneck Barnacles

The species Lepas anserifera, commonly called Gooseneck Barnacles, is found in the Order Pedunculata and found throughout the Eastern Pacific, Gulf of Mexico and Western Atlantic Ocean. Its generally found in clusters and attached to rock, wood pilings, floating material and other hard-based substrate, including whales, and live their lives attached to one spot.

This filter feeder is rarely seen in the trade, however, if living near their locations they can be collected and maintained in aquaria under the right conditions. Those would include very good water movement (WM 3 - 4) and high concentrations of plankton-like foods. There are many plankton type foodstuffs available, such as the Marc Weiss product Combo-Vital and those from Reed Mariculture that may suffice, however the amount required to maintain these creatures would cause very nutrient rich surroundings which could generate copious amounts of algae. Heavy protein skimming would be advised, as would frequent water changes.

Volcano Barnacles

The species Tetraclita stalactifera is found in the Order Sessilia and they also abound in the same areas as does the above species. Even though not purposely collected for the trade, this is a very common rock-dwelling species and quite similar to those found in many other worldwide locations at low tide. It can actually fair quite well out of water for long periods of time, such as in-between tidal flows. If collected, the same care as mentioned above is required.


As to these shrimp-like creatures they fall into the Subphylum Crustacea which has over 32,000 described species including many yet undescribed species, and which has many species of interest to aquarists. For what its worth past thinking had the Order Decapoda (shrimp) placed in the 'Phylum' Crustacea, which was then divided into two suborders, 'Nantantia' containing the more interesting shrimp, and 'Reptantia' containing lobsters, crabs, and hermit crabs. The latest thinking is that 'Crustacea' should now contain six classes and be a 'subphylum' of the 'Phylum Arthropoda.'

Only a few of those 'classes' are of interest to hobbyists. Barnacles, which is in the Class Maxillopoda, is discussed above. The remaining two classes of major interest are Branchiopoda and Malacostraca, which contain by far the majority of animals we hobbyists think of as crustaceans. Those in the Class Branchiopoda are mostly freshwater or brackish species, such as brine shrimp, usually incorrectly called Artemia salina, as this species is thought to be extinct. Yet one of the known species from the San Francisco area, Artemia franciscana, is regularly cultured for the aquarium trade. Another, the very common Daphnia pulex, which would be familiar to freshwater aquarists, is however also used as a marine fish food.

Nevertheless, those in the Class Malacostraca are of far more interest as it contains crabs, lobsters, prawns, shrimp, and crayfish. It's further divided into three subclasses, Phyllocarida, Hoplocarida and Eumalacostraca. As for Phyllocarida, its mostly ancient/primitive creatures, with most extinct. In the Subclass Hoplocarida, its Order Stomatopoda contains those dreaded mantis shrimps that are often undesirable in our aquariums.

In the Subclass Eumalacostraca, there are several superorders, two of which are of interest to marine aquarists. Its Superorder Peracarida contains small bottom-dwelling isopods and amphipods, along with small opossum shrimps we know as mysid shrimps.

The Superorder Eucarida contains two orders of significance. Order Euphausiacea contains the Pacific Krill (Euphausia pacifica), which is an excellent foodstuff, either frozen or freeze-dried for our fish. And probably the most interesting is the Order Decapoda (meaning ten feet), which includes shrimps, prawns, lobsters, hermit crabs, and true crabs, and is composed of about 68 families containing almost 10,000 species.

This order is further divided into two suborders, Dendrobranchiata and Pleocyemata where those within it are classified by the structure of their gills and legs, and the way larvae develop. Those in the Suborder Dendrobranchiata release their eggs into the water and hatch as nauplii. And if shrimp are a people food in your household, a whole industry has been built around the culture of 'prawns' in this suborder. As for those in the Suborder Pleocyemata, its members cement their eggs to their pleopods (abdominal appendages) until they hatch, and these are of more interest to aquarists.

And once we move into the Suborder Pleocyemata, there are numerous 'infraorders' dedicated to various types of creatures, e.g., shrimp, lobsters, crabs, etc., and two have special interest if 'ornamental' type shrimp are of interest. In the Infraorder Stenopodidea, Family Stenopodidea, there's a very familiar species called the Banded Coral/Boxer shrimp Stenopus hispidus. However, it's not technically considered a shrimp! It's considered more a lobster-like creature. And the Infraorder Caridea is where the more familiar 'true shrimp' genera begin to show up.

As to hobbyists, they mostly think of shrimp in general as "cleaner shrimp" and well suited for the community aquarium. Nevertheless it's necessary to know what shrimp are safe with other invertebrates. And one of the more valuable and interesting crustaceans in this order 'is' cleaner shrimp, i.e., those that participate in the phenomenon of a cleaning symbiosis. This event involves the removal of parasites and other matter from various body parts of infested fish, all in the name of a square meal. Their grooming/cleaning habits include climbing into the mouth of fish, cleaning their teeth and gill area and/or picking small pieces of diseased flesh/bacteria from along the sides of the fish. To signal the willingness of the shrimp to perform the cleaning ritual they perform either a rocking motion or swaying of their antennae and/or front legs. Since community aquariums sometimes contain large fishes like angelfish, triggerfish, etc., which in turn like to eat shrimp, having both together in the same aquarium is a chancy situation, especially where the shrimp is concerned. Even placing shrimp in the reef aquarium where fish species are usually less aggressive, is still chancy. Not chancy for the shrimp, but chancy for other invertebrate as some shrimps have a tendency to pick on corals and anemones. Yet, if wanting to keep shrimp, the best habitat is that of a reef tank.

A question that arises every so often is what types of cleaner shrimp can be safely kept together in the same aquarium. Of the three most common, i.e., Lysmata, Periclimenes, and Stenopus, only the L. amboinensis and L. grabhami would be recommended as being safe to keep together in the same 'average size' aquarium. Even then sufficient hiding places and a good supply of food is necessary to keep them from consuming each other. In larger aquaria with many hiding places and a good supply of food, different species can be maintained in the same environment.

As for molting in general, i.e., the shedding of its shell-like exterior (exoskeleton), its an extremely important growth aspect for all shrimp. To grow larger, shrimp must shed this exoskeleton as it will not stretch. Periodically the shell-like covering begins to dissolve and separates from the body tissue while a new shell develops underneath. When the process completes, the shrimp climbs out of the old exterior covering and then takes up water, stretching the new soft covering to fit its now larger body. When finished, the new covering forms a hard exoskeleton. They are defenseless at molting time; therefore need secure hiding places that predators cannot reach.

Keep in mind all new shrimp additions should be slowly acclimated to their new surroundings as they have a tendency to go into shock when entering an aquarium where water parameters are only slightly different from the shipping container. Temperature and especially specific gravity should be the same before transferring them into their permanent home. Contrary to what you may have heard, shrimp of any kind should never be given a freshwater bath to kill parasites prior to being added to the aquarium. It 'will' kill them, as they are very sensitive to changes in osmotic pressure. And as with all shrimp, low alkalinity, calcium, iodine and especially low magnesium levels can interfere with the molting process. In fact, magnesium 'must' be maintained at the proper level in relation to the specific gravity or the molting process will not complete. The lack of proper magnesium level is probably the main reason why many aquarists fail to maintain shrimp over the long term!

Lets now simply stay with their 'Family' classifications and move through those of interest. Keep in mind, mysis, krill, copepods, and amphipods were already discussed in Chapter 14.

Family Hippolytidae

There are several commonly available shrimp species, all quite attractive, with the Scarlet Cleaner/White-striped/Skunk Shrimp L. amboinensis the most popular. It hails from the Tropical Indo-Pacific from the Red Sea to Hawaii and is found in coral reef environments, e.g., reef caves, holes, and ledges from 3 – 35 feet (1 -10 m) in depth.

This beauty has two red longitudinal stripes separated by a white stripe that terminates in a white-blotched inverted "T" on the tail fan. It also has extremely long white antennae. This 3 inch (8 cm) cleaner shrimp can be kept in small groups and will come directly onto the hand to take pieces of clam, shrimp, krill, mussels, frozen mysis, fresh fish flesh and the hair off the back of your hand. It is frequently in view during the day, yet may pick/steal food from corals, but does not seem to be destructive. Since these shrimp are hermaphroditic spawners (possess both male and female sex organs), all adult members of the group produce eggs and are fertilized by another member of the group. Therefore, any two of these shrimp is sufficient to propagate the species, if they like each other! Readily breeds in the home aquarium, yet do not yet know of the availability of captive-bred specimens. In aquariums, most of the larvae are either eaten by fishes or drawn into filters. They seem to be sensitive to temperatures above the low eighties.

There's also an Atlantic morph, L. grabhami, sometimes called the 'Candy Cane Cleaner Shrimp or Caribbean L. amboinensis,' that is almost an exact copy, except its white tail edging is continuous on both edges.

Another very popular species is L. debelius, (usually called the Blood Red Shrimp. It hails from the Indo-Pacific Ocean: Society Islands, Japan, and the Maldives and is found in coral reef environments in shaded areas with overhangs. It will set up cleaning stations, but due to their shyness, spends most of their time hiding in caves. Usually somewhat highly priced. In large aquariums, one may lose sight of these 2 inch (5 cm) shrimp for months. They generally come from the Indo-Pacific, yet the ones from the Maldives seem to be slightly larger, have a deeper red color, and very long antennae. They will accept defrosted pieces of clam, fresh fish and shrimp flesh, or live brine shrimp. Yet, it is difficult to tell if they are getting their share of food because of their intense shyness.

There is one further species in this genus, L. wurdemanni, the Peppermint Shrimp, Caribbean Cleaner Shrimp, or Veined Shrimp, which hails from the Tropical Western Atlantic Ocean: Gulf of Mexico, and the Caribbean. This small, about 1.5 inch (4 cm) shrimp, inhabits shallow coastal reef areas rich in pipe-shaped tube sponges and lives singly or in pairs, usually inside their hollow interiors or in nearby crevices and small holes. Basically nocturnal and feeds upon various forms of zooplankton that become trapped or adhered to various forms of substrate in the area, including the surface area of sponges. Generally safe for reef aquariums and usually purchased in small groups because they are a very good eliminator of unwanted Aiptasia anemones. Another species that is quite similar in many ways is L. californica, e.g., color/living conditions, and which hails from the Eastern Pacific and the Gulf of California. However it does prefer slightly cooler waters.

Provide numerous hiding places as once the species is in the aquarium they will seek out hiding places and rarely be seen during daylight hours. It is not necessary to feed them as they hide mostly by day, usually on the underside of elevated rocks, and scavenge/feed during the night. However they appear to have a taste for zoanthids such as Parazoanthus gracilis, which is generally called Yellow Polyps by aquarists..

Note this species molts about every seven months. Keep in mind they are defenseless at molting time, therefore need secure hiding places that predators cannot reach. It also begins life as a male, yet most change to females, however, they retain the male ducts and produce sperm. Therefore the females are able to incubate their own embryos without the help of a male. Has been successfully captive bred. There are also three look-alikes coming from approximately the same areas, L. ankeri, L. bahia, and L. boggessi that infrequently show up and are confused with L. wurdemanni as they are 'very' similar in coloration and size. All are usable in the aquarium.


There are a couple of species; S. marmoratus the Marble Shrimp, and S. neglectus the Green Marble Shrimp that are occasionally available. They are Indo-Pacific species and are fairly hardy and do well, except in reef aquariums where their favorite meal is coral polyps. They get to about 4 inches (10 cm) and are solely nocturnal animals with the ability to change colors to match their background. Yet, they are usually a mottled green, becoming a light red at night. These should be maintained singly or in mated pairs. Males have much longer foreclaws than females, sometimes as long as their body. The female has a very pronounced curved abdomen. NOT SAFE WITH CORALS.


This small shrimp, T. amboinensis, about .5 inch (1 cm) with the common names Anemone Shrimp or Sexy Shrimp, is extremely popular with aquarists. It is a circumtropical species and usually found in coral reef environments living with anemones, such those in the genus Heteractis. It does not seem to be necessary to feed them, as they appear to feed upon the mucus generated by various anemones and corals, and seem fond of those found on zoanthids without harming them. The female is larger than the male. It is also often found living with the shrimp in the genus Periclimenes. Can be easily maintained in a very small aquarium, i.e., less than 10 gallons. Not a cleaner shrimp.

Family Alpheidae
Pistol Shrimp

Even though there are a number of different members, they all make the same noise, a sound similar to a 22 caliber shot. Hence their name "Pistol Shrimp." They do so by snapping the fingers of their single, yet exceptionally large claw. Most are very small, less than 2 inches (4 cm) or less in body length. They are nocturnal creatures, usually hiding during the day under a rock until dusk. At night they come out and search for food and use the large claw to either scare away intruders or shock/stun other mealtime small crustaceans. Usually arrive on live rock and the only way you'll ever know one is in your aquarium is by hearing these single shot sounds, probably when you are trying to sleep! Some live in a symbiotic relationship with watchman gobies.

Family Gnathophyllidae
Harlequin/Clown Shrimp

This very interesting and beautiful species, Hymenocera picta, grows to about 2 inches (5 cm) and hails from the Red Sea and the entire Tropical Indo-Pacific from East Africa to Hawaii. They feed 'only' on live starfish. I say, "only on live starfish," as they will not take dead or frozen ones. You'll need a fresh live starfish, preferably the genus Linckia (Blue Stars), and they tend to consume one every four to six weeks. Seeing a starfish torn apart and almost completely eaten may not be the thing you want to witness in your home aquarium! Besides being carnivorous, they are very territorial. Therefore only one or a mated pair can be kept in the same aquarium. There is some thought there may be another similar species (H. elegans), which is said to be more reddish than H. elegans. Requires a temperature above 77°F.

Family Palaemonidae

Periclimenes holthuisi

Hails from the Red Sea to the Indo-West Pacific and as far as Australia. A very small 2 cm shrimp with a translucent body with white spots and flecks. Tips of its claws and the telson have bluish purple bands. Lives in a symbiotic association with various anemones and also some long tentacle corals, e.g., Catalaphyllia jardinei and Heliofungia actiniformis. In aquaria, needs a host anemone or coral. Has a temperature range of 73 to 83°F (23 – 28°C). Depends upon the cleaning process for its food. Difficult to maintain in the aquarium, especially if there are large fish. Will have to leave the anemone when it molts, therefore can easily be eaten by larger fishes.

Family Rhynchocinetidae
Camel/Dancing Shrimp

Even though the genus Rhynchocinetes contains a number of different species, R. durbanensis is often the most commonly imported from Sri Lanka, Indonesia and the Philippines. It has a pale red body with numerous white lines and spots and reaches about 2 inches (5 cm). Hides mostly by day, usually on the underside of elevated rock. It comes out at night to feed and has a taste for zoanthids and flower coral, and will occasionally pester or pinch other soft and stony coral. This may simply be in search of food or the cleaning of certain pests from corals, but be forewarned, usually not acceptable for the reef aquarium. Should be maintained in small groups of five to ten, where the males will set up small harems. Difficult to feed because of its shyness. Sinking shrimp tablets make a good foodstuff. Similar in appearance to R. uritai, which is rarely imported as it comes from South Korea south to Japan and is found in cooler waters.

Family Stenopodidae
Banded Coral/Boxer Shrimp

The species Stenopus hispidus is widely known as the Banded Coral or Boxer Shrimp. It hails from all tropical seas and is found in coral reef environments and generally wherever there are caves and holes. Its one of the favorites among aquarists and are easily kept in the reef aquarium when there is sufficient hiding places. But it can do harm to corals and anemones when there is insufficient food. It attains a maximum size of 4 inches (10 cm) and is equipped with three pair of walking legs, with two very strong pincers. They will also set up cleaning stations, but seem to be infrequent cleaners in the aquarium and should be maintained singly or in mated pairs. The female has a heavier body, carries her eggs for about two weeks under her shell. The eggs can usually be seen through the shell where they are first a yellow color, then turn a light green. When the female molts, about every 16 days, the eggs are fertilized by the male. The eggs are hatched in the female's mouth in small numbers about two weeks later and released into the water column. The baby shrimp are half the size of newly hatched brine shrimp and can live on their yolk sac for three days. Rotifers are a good food supply until the babies can take larger food. Adults accept defrosted pieces of clam, shrimp, krill, fresh fish flesh, or live brine shrimp. Technically, it's considered more a lobster-like creature than a shrimp.

Mantis Shrimp

The Order Stomatopoda contains one of the most dreaded shrimp in any aquarium that contains fish or invertebrate. Generally, they show up as hitchhikers hidden in holes inside live rock. Some can get quite large, and have personally seen specimens that appeared to be about 10 inches (25 cm) in Mexico waters. They look quite similar to their terrestrial counterpart the "Praying Mantis" hence their name. These are awesome predators, and are armed with powerful appendages that can destroy hard-shelled prey. They can easily smash the shells of snails, crabs, clams, easily capture fish, eat feather dusters/hard tube worms, and can split your finger right down the middle! Pistol Shrimp make a sound similar to a single 22 caliber shot, however, mantis shrimp also make a noise, yet theirs is more like a machine gun, i.e., having a series of slightly less loud shots. It a good way to tell whether it's a mantis or pistol shrimp!

If the rock its living in can be removed from the aquarium, submerge it in a pail of club soda, and the shrimp will quickly leave its hole as it can no longer breathe since the club soda is nothing but water and dissolved carbon dioxide. If the rock can not be removed, plug its hole with another small stone, or fill the hole with the same type of glue that is used for cementing coral frags.

Family Odontodactylidae
Peacock Mantis

This one species, Odontodactylus scyllarus, is purposely collected for the trade, as its name is a good indication of its colors. It hails from the Eastern Pacific and is usually found on rubble covered bottom areas and grows to 12 inches (30 cm). If maintained by itself in a small 20 to 30 gallon aquarium with sufficient bottom sand and live rock for hiding places, it makes for an extremely interesting display. Provide enough loose rubble and/or caves, and if not happy with its surroundings, it will rearrange the contents of the 'entire' aquarium to suit itself. Requires daily feedings with meaty foodstuffs. Has a temperature range of 68 to 72°F (20 – 22°C).

Clawed Lobsters

The word 'lobster' applies to members of two very different decapoda infraorders, Astacidea and Palinura. Both have bodies that are covered by a hard integument or shell. They are shaped for swimming and crawling using legs, not pleopods as do shrimp, and have a flattened abdomen area. Those in the Infraorder Palinura are the spiny lobsters, more a local human food species than for aquariums. Those in the Infraorder Astacidea are clawed lobsters, and not closely related to spiny lobsters, slipper lobsters or squat lobsters, which have no claws. The closest relatives of clawed lobsters are in the genus Enoplometopus, which are somewhat popular in the marine aquarium trade. There are a couple species that show up in the trade.

Family Enoplometopidae
Polka-Dot/Pink Spotted Lobster

The species, Enoplometopus debelius is found in waters from Hawaii to Indonesia and inhabits rocky coral reef environments. It has a temperature range of 68 to 79°F (20 – 26°C), and even though it comes from the Indo-Pacific and Hawaii most are imported from Indonesia and the Philippines. They get about 4 inches (10 cm) and have a purplish hue with deep violet markings on the abdomen. Safe with anemones and corals, but not with small fish. As with most lobsters they are extremely shy and once in the aquarium prefer to hide in caves during the day. After the lights go out they will search for food, including small fish.

Red Lobster/Hawaiian Lobster

This is another in this family that is seen in the trade occasionally and this species, Enoplometopus occidentalis has a wide range, from Hawaii across the Pacific to the Indian Ocean and south to South Africa. Yet it remains mostly exported from Hawaii. As with most lobsters they are extremely shy and once in the aquarium prefer to hide in cave areas during the day. After the lights go out they will search for food, including any small fish in the aquarium and it may also damage anemones and corals. They are small, usually about 4 inches (10 cm), all red with some pale white spots and will accept any type of fish or shrimp flesh. Undemanding when it comes to water quality. Unless you have a mated pair it is unsafe to keep more than one in the aquarium.

Hermit Crabs

The Infraorder Anomura relates to hermit crabs and other related species of which only a few are suited for the aquarium. As for hermits the more valuable species forge on various kinds of algae and detritus. Some are quite large and can be considered bulldozers, knocking things over in the aquarium and becoming destructive. Some of the larger hermits are omnivores and may nip at corals; therefore they are not recommended for reef systems. Yet there are some small hermits, mostly from Mexico, Florida, and the Caribbean that are beneficial, especially in aquariums with a sandy bottom as they turn over the upper level of sand grains keeping it clean looking while looking for a meal. Unfortunately some eat coralline algae, a favorite alga amongst reef keepers. Keep in mind if the supply of algae is quite limited, an algae wafer or feeder block may help supplement their diet.

It's also important to keep an assortment of slightly larger empty shells scatted around the sandbed surface because as they grow in size they need a larger shell to protect themselves from predators. They may also sometimes pick on snails, however it is thought they are simply checking out its shell and not attacking the snail itself.

Family Diogenidae

There are many genera and species of interest in this family; some are excellent scavengers, while others may be dangerous to other animals in the aquarium. Lets first begin with those not suited for the reef aquarium or small fish-only systems, and those are in the genus Dardanus.


Probably the most common in the trade is D. megistos, sometimes called the White-spot Hermit. It hails from the Indo-Pacific where its found in shallow lagoons and bays, and can reach 8 inches (20 cm) in length. Its bright red hairy legs make it look quite attractive, especially when small, but it's capable of catching small fish while they are sleeping. Another watch item is D. pedunculatus, called the Coral Hermit or Anemone Hermit, which is about 4 inches (10 cm) and carries small sea anemones on its shell. When it switches shells, it removes the anemones from its old shell and places them on its new shell. It's also not trustworthy in reef aquariums or where small fish are tankmates, as they may become dinner.

Striped Hermit

This attractive hermit, Trizopagurus strigatus comes from the Indo-Pacific and Red Sea. It's a medium size hermit, about 3 inches (7.5 cm) that is not suited for the average reef aquarium, basically because it's a bulldozer. Better suited in large fish-only systems or large reef systems with large inverts and fishes.

Lets now move to more desired species in this family.


There are two excellent species in this genus, C. elegans the Blue-banded Hermit, and C. tibicen the Orange Claw Hermit. The first comes from the Western Pacific, and has bright blue bands on its legs. It picks at algae, including coralline and cyanobacteria and is a fairly good mover of sand surfaces, but has a tendency to crawl over coral disturbing but not harming them. It's not often seen in the trade. The second comes from the Western Atlantic intertidal zones and has orange legs and blue eyes and picks at micro and macroalgae, and decomposing matter. It's more active during the day and spends most of its time on rocks and is safe for use in the reef aquarium. Both are only slightly larger than 1 inch (2.5 cm).

Blue-legged/Tri-colored Hermit

The species Clibanarius tricolor comes from the Western Atlantic Ocean, Caribbean, and Gulf of Mexico. These small, less than 1 inch (2 cm) hermits have orange-brown legs, black and white claws, and a bright orange face with sky-blue eyes. It's a good sand stirrer, besides feeding on detritus, microalgae and slime algae, and is safe for use in reef aquariums.

Scarlet Leg/Red Legged/Scarlet Reef Hermit

The species Paguristes cadenati comes from Western Atlantic Ocean, from Florida to the Bahamas and West Indies. It's a good bottom scavenger, especially in reef aquariums, however, some seem to dwell more on rocks where picking at algae appears easier to get at. They do not harm coral polyps and don't get much bigger than 1 inch (2.5 cm). They have a bright red body and yellow eyestalks, and also seem to like coralline algae, but do not stay in one place long enough to do much harm with any damaged areas usually re-grown within a couple of weeks. May be more nocturnal when first introduced.

Family Paguridae

There are two in this genus, both from the Western Atlantic's intertidal zones, P. holthuisi called the Red-stripped Hermit having white eyestalks with grayish-blue eyes, and P. operculatus called the Polka-dotted or Dwarf Blue-leg Hermit. Both are fairly good hermits for the reef aquarium.

Family Porcellanidae
Porcelain Crabs

Porcelain crabs are not true crabs, as they are more related to squat lobsters, which I've skipped discussing here as they are rarely seen in the trade or maintained in captivity. True crabs have relatively immobile tails, however, porcelain crabs can use their broader tails for swimming. They also have flattened bodies and claws, and probably get their common name because when threatened by a predator, they shed or break off their claws. Their feather-like legs in front of their mouth are waved through the water to gather planktonic-like food.


Two in this genus show up in the trade, although quite infrequently, and both hail from the Indo-Pacific. Both are suspension/filter feeders about 1 inch (2.5 cm) in width. The first, N. maculates live in pairs and is basically white with 'many' tiny brownish-orange spots. It's often found on the genera Entacmaea, Stichodactyla, Cryptodendrum, and Heteractis sea anemones. The second N. ohshimai, is simply called the Anemone Crab. It's basically white with an irregular pattern of orange spots and is also found having a symbiotic relationship with various anemones, sometimes even those called mushroom anemones. They should not be kept with tube anemones, as they will be stung to death by its long tentacles. As for feeding, frozen plankton and/or powdered flake foods fed once daily will suffice nicely.

True Crabs

These are in the Infraorder Brachyura, possess flattened bodies, an abdomen located on their bottom side, and short antennae. They are not fussy eaters, usually free from diseases, and are mainly carnivorous. There are members of many different families and genera that occasionally show up in the trade, nevertheless, only three species are commonly available. That's probably good, as anything with a claw should be researched quite well before putting it into the aquarium.

And for those that have to be removed, it's a question I've fielded numerous times. The best way to rid unwanted specimens comes with using a large tall glass, similar to a drinking water glass. Simply bait the glass with a tasty morsel and place the upright glass at the aquarium bottom touching some rock in the evening. The crab will sense the food and using the rock surface, gain entrance to the glass. Because the glass has smooth sides, it won't be able to climb out. Not always 100% effective, but has resolved some terrible crab problems.

Family Hepatidae
Shamefaced Crab

The species Hepatus epheliticus, hails from the Caribbean, and are called 'Shamefaced' crabs because they hold their large claws in front of their face. During the day they are hidden in sand and after nightfall come out to search for snails, their favorite meal. They rarely appear in the trade, but beware, unless you have a never-ending supply of snails this is nothing for the home aquarium. They also will eat clams and other mollusks.

Family Lithodidae
Golden King Crab

The species Paralithodes rathbuni, hails from the lower coast of California down into Mexico and almost always is referred to as the Golden King Crab. Has no commercial value, and is usually found among rocks in deeper waters. Nevertheless, its spidery appearance and yellowish legs and body sometimes makes for an interesting oddity if one can maintain a cooler water aquarium, as its temperature should not exceed 73°F (23°C). Almost any type food is accepted.

Family Plaqusiidae
Sally Lightfoot/Nimble Crab

This species, Percnon gibbesi, hails from Tropical East & West Atlantic Ocean from the Azores to Cape of Good Hope and from North Carolina to Brazil, and also the Eastern Pacific Ocean from Baja California to Chile.

This flat-bodied species with a greenish-maroon body is a strong swimmer and is usually found living on rocky coastlines where rock surfaces and rubble are algae covered. Younger members feed upon algae, whereas more mature members also feed upon small fish and various crustaceans and other small invertebrate.

This fast moving crab is often sold as a herbivore, yet larger specimens, i.e. about 3 – 4 inches (7.5 – 10 cm) in diameter (from leg tip to opposite leg tip) are predatory creatures. They will eat small crustaceans, fish, hermit crabs, and may injure some corals, and also decorative anemones while attempting to gain access to the materials in the gut. This is not a reef safe animal, and even if kept in a fish-only aquarium, thought must be given to what size and type fish and invertebrates are in the system. A herbivorous crab that will eat both.

As for feeding, they are not fussy eaters, as small members will scavenge various forms of algae (macro and microalgae including short tuffs of hair algae), but more mature ones are a predatory hazard as they may attack small fishes while they sleep. There are no special feeding requirements for this crab.

Family Mithracidae
Emerald Crab

This species, Mithrax sculptus is often sold as a herbivore that can reduce unwanted algae problems, especially bubble algae, e.g., Valonia spp. making it quite popular on some fronts in the hobby. It hails from the Tropical Western Atlantic Ocean from Florida to Brazil, including the Caribbean and the Bahamas and is found in intertidal zones. They have a shiny green carapace and claws, with hairy, dark green walking legs. Their claws have blunt tips, which are used for feeding on different forms of algae. Nevertheless, they are not totally reef safe organisms since in the wild they also live on coral polyps. Probably a much better choice for a fish-only system having an algae problem. Males have larger claws, therefore may be better algae eaters.

Family Inachidae
Decorator Crabs

There are two species that make it into to the trade, Camposcia retusa (this Family) and Cycloeloma tuberculata (Family Majidae), which hail from the Indo-Pacific that are commonly called 'Decorator' Crabs. The first is generally found in mangrove areas, estuaries and rocky areas. They adorn their carapaces with bits of sponges, algae, and bryozoans, and in doing so, almost look like a big hairy tarantula spider. Even though safe for most reef aquariums, they do have an appetite for feather duster worms.

As for the second species, coming from intertidal zones and shallow lagoons, it covers itself with small anemones and sponges and has a yellowish fuzzy-like body and claws. It's sometimes referred to as the Teddy Bear Crab and it will clip off bits of coral, anemones, other crabs, and algae to 'decorate' itself. Cannot be trusted with small fish or any invertebrates.

Spider/Arrow Crab

This spider-like crab, Stenorhynchus seticornis, is one of the more interesting crabs that are seen in some marine aquariums. It has a cone-shaped body with long spider-like walking legs, with the first front legs each having a well-developed claw.

Since they are very aggressive towards each other, only a mated pair can be kept together. They should not be kept in any aquarium that contains feather dusters or tubeworms. Worm steak is always on their menu. Have also seen them snip off a pieces of mushroom polyps. Not really safe with some soft corals, e.g., Xenia, zoanthids, and of course, mushroom corals. Otherwise, they appear to be fairly safe in the reef environment. They are also small bristle worm consumers. Those seen in the trade usually hail from the Tropical West Atlantic and the Caribbean. And they are not fussy about water quality. In the wild they often are found close to anemones, even stinging anemones, which they use for cover if danger approaches. They appear to be immune to their sting.

Family Trapeziidae
Coral Crabs

There are several species in this family that have small crabs living on the branches of stony corals, e.g., Acropora, Stylophora and Pocillopora. They can also be considered hitchhikers, as they are not normally sold separately. They feed on the mucus secretions of their host coral and do not seem to do any harm. Consider them freebies and an interesting species to watch.

Family Xanthidae

There are a few species in some of the various genera in this family that occasionally make it into the trade and show up at local shops.

Boxer/Pom-Pom Crab

The species Lybia tessellata hails from the Tropical Indo-Pacific from East Africa to the Marshall Islands where it inhabits intertidal and rubble zones, and usually is found under dead coral. These pretty little animals, about 2 inches (5 cm), are basically detritus consumers. Yet would not trust them in the same tank with shrimp. They sometimes put small anemones (Bunodeopsis spp.) on their claws and wave them at approaching enemies, hence the name "Boxer Crab." Probably not suited for the large reef tank as it likes to hide, but in smaller systems it can be easily maintained with small pieces of meaty foods.


There is no known common name for the species Z. aeneus, except possibly the 'Scavenger Crab' as it's an excellent scavenger of any leftover foods. This species has deeply ridged zones on its carapace and is often spotted with red, and sometimes light blue, nevertheless, its coloration is often varied making a sure ID somewhat guesswork. It has thick and strong claws, and if that were not enough for hobbyists to shy away from this species, it contains a deadly poison (Saxatoxin) that even in tiny amounts is deadly to humans. A good scavenger, yet cannot be trusted with invertebrate, but is safe in fish-only aquariums.

Family Pilumnidae

Bristle Crab

This brownish-greenish crab, Pilumnnus hirtellus, has bristles on most of its legs/claws. Widely distributed and usually arrives on live rock from various areas and can get to about 1 inch (2.5 cm). Have seen what appears to be the same crab in Mexican waters, yet somewhat larger. Eats everything it can get a claw on and is one of the crab hitchhikers that should be removed as soon as it's seen. In fact, any of these bristled crabs are not to be trusted!

Phylum Chelicerata

Family Limulidae
Horseshoe Crab

Even though this Phylum has nothing to do with crabs, there is one member in the Order Xiphosura that interests some marine hobbyists and that is the Horseshoe Crab, or sometimes called the King Crab, Limulus polyphemus. Actually, it's not a crab, as it is more closely related to scorpions and spiders. In fact, they have remained unchanged for 350 million years. It is mentioned here only because it is one of the better sand stirrers. Small juveniles, less than 6 inches (15 cm) are fine for aquariums containing a sandy bottom. Finely diced squid, fish, live brine shrimp, along with some algae to graze on is generally sufficient for its needs. Sinking shrimp meat tablets are also a good foodstuff. Yet beware, it can attain a size of about 2 feet (60 cm) in the wild.

They have ten eyes, with two easily seen on the top shell with eight other small and simpler eyes on the shell (carapace), a gill structure that allows them to remain out of the water for several hours (usually while breeding) and blue blood as it lacks hemoglobin. Instead, they use hemocyanin, a copper based compound rather than an iron based compound for absorbing oxygen. It's spike-like tail does not bend or flex, and is used for turning itself over if flipped over by a wave or other animals.

Found along the Gulf and Atlantic shorelines of the United States. When small, it's safe for use in reef aquariums, and does better in systems with a deep sandbed with lots of open sandbed surface areas.

Phylum Mollusca

Molluscs (British spelling) or mollusks (American spelling) are a large collection of animals, e.g., over 110,000 living species. They are known for their decorative shells and mantles such as with clams and abalone, and/or squid, cuttlefish and octopus, which are one of the more intelligent invertebrates known to man.

Mollusks have a mantle that is simply a fold of the outer skin lining the shell and a muscular foot that is used for motion and/or securing the individual. In many species, the mantle produces a calcium carbonate external shell and their gill extracts oxygen from the surrounding waters and also disposes of wastes. All have a complete digestive tract that begins with the mouth and terminates with the anus. There are many having a teeth-like structure for feeding, i.e., the radula, which is composed mostly of chitin. These 'structures' are used to scrape algae off rocks, and also in the harpoon-like structures of cone snails. Squid, octopus, and cuttlefish also possess a chitinous beak.

There are ten classes of mollusks; two consist of fossilized members, i.e., Rostroconchia and Helcionelloida; and Caudofoveara and Aplacophora that contain deep-sea worm-like creatures; and, Monoplacophora which contains deep sea limpet-like creatures, and also Scaphopoda which relates to Tusk Shells, and all are not of special interest to aquarists and divers. Therefore species in those six will not be discussed here. However, those of more interest are:

Class Bivalvia (also Pelecypoda) - clams, oysters, scallops, mussels

Class Polyplacophora - chitons; 600 species, rocky marine shorelines

Class Gastropoda - nudibranchs, snails and slugs, limpets, sea hares; sea angel, sea butterfly, sea lemon

Class Cephalopoda - squid, octopus, nautilus, cuttlefish

Class Bivalvia - Clams

This Class contains approximately 30,000 species, and includes scallops, clams, oysters, and mussels. Several have major interest amongst reef aquarists.

Family Limidae
Flame Scallop

There are two species in this genus, Limaria fragilis hailing from the Western Pacific and Australia, which is sometimes simply called the Fragile File Clam, and that of L. scabra coming from the Western Atlantic and Caribbean to Central America, which is always called the Flame Scallop. Nevertheless, I've seen the first also being sold as the Flame Scallop. Both inhabit shallow reef environments and are found embedded among rocks and coral rubble

Has a temperature range of 72 to 83°F (22 – 28°C) and mentioned here because it persists to be available in most stores. It has the ability to swim by opening and closing its shells and expelling water from its internal cavity like a jet engine expels air. They also have a row of tiny eyespots around the edge of the mantle similar to the Tridacna clam, which helps them escape predators by jetting away when moving shadows are detected. Flame scallops are pretty; yet do not usually last much longer than six months in captivity. They also like to flit here-and-there, sometimes knocking things over.

Keep in mind once in the aquarium they prefer dimly lit protected places, such as areas in aquarium corners or between rocks/inside cave-like areas. So don't expect to see much of them once in the aquarium that has a lot of hiding places. As for its nutritional needs, it's a filter feeder, where in the wild it strains plankton from the waters using its gas exchanging gills to also filter out plankton. The hair (cilia) covered gills create water currents within the gill structure to enable good gas exchange across the gill structure and also move food particles collected on their surfaces through the gills into channels that lead to the clam's mouth. Since it does not contain symbiotic algae, as do tridacnids (giant clams), it requires it be fed a supply of preserved and/or live phytoplankton 'at least' once daily as they are complex creatures containing hearts, stomachs, gills, gonads, intestines, etc., therefore burn a lot of calories to remain healthy! I have used products like American Marine Selcon or Marc Weiss Combo-Vital that can produce nutritious suspension matter to help extend their stay in aquariums and also various plankton-like products from Reef Nutrition. (WM 2)

Family Tridacnidae
Tridacna Clams

There are two genera of interest: Tridacna and Hippopus. Those species of more interest are Tridacna maxima, T. derasa, T. gigas, T. crocea, and T. squamosa. Hippopus hippopus is rarely seen in the trade, as is T. mbalavuana (= tevoroa) and H. porcellanus. As for T. rosewateri, a possible ninth in the family, it is yet proven and there are no known photos of a live specimen. And yes, there are some shells thought to be the species, but those may simply be the shells of an odd-shaped maxima. When it comes to size 'in the wild,' T. crocea is about 6.5 inches (16 cm), T. maxima about 12 inches (30 cm), and for Tridacna gigas about three feet (1 Meter).

These photosynthetic animals are naturally found in the Tropical Western Pacific and Red Sea to Eastern Africa with the more colorful clams high up on reef areas where there is intense light and excellent water movement. Those in fairly shallow areas have a highly pigmented mantle that shields them against damaging UV. Actually, it's these colors, i.e., blue, green, and yellow hues of their mantles that point to those that exist in shallower waters. Those of the species T. gigas and H. hippopus indicate deeper water specimens because of olive-green mantles, as does the typically brownish-green mantle of T. derasa.

The two shells that form their enclosure are hinged and held together by a powerful muscle. The mantle has two openings, one is an inlet siphon and the other is the outlet siphon. Water and some water borne nutrients enter the clam through the inlet siphon, which is slit-like in the mantle (indicates a healthy clam, as a wide open inlet siphon indicates a stressed clam which needs your attention!). Excess water and waste are expelled through the tube-like outlet siphon also located in the mantle. They also have primitive "eye spots" along the mantle's outer edges that can detect changes in light intensity.

Strong water movement brings suspended particles and nutrients and at the same time its zooxanthellae, via photosynthesis, utilize a portion of the clam's own waste products for food. In return the alga waste products provide a natural food source, i.e., carbohydrates/glycerol for its host. These clams actually make about 90% of their own food requirements. Their dinoflagellate zooxanthellae have been identified as Gymnodinium microadriaticum and excess cells also serve as a food supply. However they are also filter feeders, yet any attempt at specialized feeding with planktonic type food appears to be fruitless. Therefore adequate lighting, e.g., about 6 – 8 hours per day, is extremely important in the health of these miniature algae scrubbers. Excellent lighting, good water movement, properly dosed calcium, magnesium, and iodine additions will provide long term success with these giant clams. (PAR 400+) (WM 2 - 3)

There are two predators to be aware of: a small white cone-shaped snail, Pyramidellidae sp., about one eight of an inch (1 - 2 mm) that sucks the juice out of its mantle. Multiplies quickly at a very small size! In large numbers can be a serious threat to any clams in the aquarium. At nighttime, they are usually found just under the clams upper edges where the mantle overhangs. A good place to suck its juices! And possibly during the day, may be either located near the foot area or under one of the side ridges on the shell.

The second predator, Cymatium muricinum, enters the clam through the byssal opening and after consuming the juices inside the clam and killing it, then moves on to other clams. And yes, there are other clam predators such as bristleworms, starfish, and crabs, so be diligent if maintaining these beautiful clams.

The Sixline Wrasse, Pseudocheilinus hexataenia , Fourline Wrasse Pseudocheilinus tetrataenia, Christmas Wrasse Halichoeres ornatissimus, and Leopard Wrasse Macropharyngodon meleagris, may eat these snails. The Christmas Wrasse is the best at eliminating these pest snails, and also any other small snails in the aquarium (good or bad).

Since these clams attach themselves firmly to a firm substrate surface, I prefer to first brush their side with a stiff toothbrush to remove any hitchhikers or their eggs, and then place them first on the sandbed, or possibly a small dish of sand somewhere where lighting intensity is sufficient. Once I'm sure no cone snails are on the specimen, it then gets moved to its final location, usually a firm substrate somewhere in the aquarium. Keep in mind juvenile clams generally require less light than adults because they have thinner tissue. As a result the dish method is a better way to maintain juveniles at a lower light intensity until ready for permanent placement. And if ever necessary to remove a clam from a firm substrate, never simply pull it off, as you might damage the foot area beyond repair. Instead, use a credit card or razor blade to cut the byssal threads and do so as close to the attachment site as possible.

For more information about these beautiful animals see 'Giant Clams in the Sea and the Aquarium' by James Fatherree.

Class Polyplacophora

As for Chitons, there are almost 900 species in the Class Amphineura or Polyplacophora. Most are found in the intertidal zone (the 'littoral' zone) on rocks, but some species have been found as deep as 6000 meters (about 20,000 feet). They move slowly on muscular feet and cling to substrate surfaces.

Family Chitonidae
Chiton Snails

There are numerous genera, yet where aquarists are concerned; these generally small snails on a half-shell are very good microalgae grazers and they are freebies, generally coming into aquaria attached to live rock or various coral specimens. Chiton torrianus Yet once established they may even become somewhat of a nuisance, as they can easily attain entrance into pumps and clog motor impellers. Nevertheless, they are good microalgae consumers and unless causing major problems they should be considered an asset and left to do their thing.

Class Gastropoda - Snails

Snails, slugs, abalone, limpets, cowries, and conch are included in this class, which has about 60,000 to 75,000 known living species. The taxonomy of the gastropods has been evolving, and presently there are three subclasses: Prosobranchia; Opisthobranchia; and, Pulmonata. Even though there are many species of snails, few are of interest to the hobbyist. Those that are herbivorous, i.e., graze on algae, and do not harm corals are of special interest.

Family Fisurellidae
Keyhole Limpets

Very similar to Chitons, as they also have a conical half-shell appearance, except this species has a small opening in the center top portion of its shell, hence their common name. Diodora inaequalis Basically herbivores and small in size, e.g., about 1 inch or much less (5 mm – 2.5 cm). Often arrive on live rock and can be quite useful in controlling microalgae and diatom blooms. No special care is required and arrives as hitchhikers on rock and corals.

Family Haliotidae

This family contains only one genus and is found in the Atlantic, Pacific and Indian Oceans. Members, who are generally called 'Abalone,' have large ear-shaped shells with a spiral at the apex. The inner side of the shell has a mother-of-pearl layer, which is sometimes used in the jewelry business. They are algae grazers and cling to rocks with a large muscular foot, and can crawl if necessary. One species, Haliotis cracherodii is found in the Eastern Pacific and called the Black Abalone and inhabit shallow coastal areas rich in kelp. It has a temperature range of 59 to 75°F (15 – 24°C), therefore requires a cool water aquarium with a good supply of algae to feed upon. Basically shy and prefers subdued lighting. Feed various 'greens' including lettuce and algae tablets. Can sense and move towards food. Requires daily feedings and good water quality and can reach a size of about 6 inches (15 cm).

Family Neritidae
Nerita Snails

Many of these small rounded herbivorous snails often crawl out of the aquarium as they are more an intertidal species than a reef species, e.g., Puperite pupa called the Zebra Nerite. And if forced to live submerged all the time they probably won't last a year. Even though they are fairly good at trimming algae, which includes diatoms, microalgae, filamentous, and cyanobacteria, they should only be considered supplementary consumers as they really don't compare to what Astraea snails can accomplish. There are many in this family in several genera, and if of interest, recommend searching the Internet for more about these snails, as they might be short-lived in your aquarium, or at least found on the floor some early morning!

Family Trochidae
Red Foot Moon Snail

The species Norrisia norrisi comes from the Eastern Pacific Ocean: California and inhabits shallow coastal kelp areas. Has a temperature range of 59 to 75°F (15 – 24°C) and is better suited for cooler running aquariums that have algae problems as it's a glutinous consumer of hair algae. Actually, not well suited for tropical aquariums as they are truly a temperate species, however they show up in the trade.

Margarita Snail

This snail, Margarites pupillus also hails from the Eastern Pacific Ocean: from Alaska all the way down to California and inhabits shallow coastal areas. Has a temperature range of 50 to 68°F (10 – 20°C), yet has been maintained in slightly higher temperatures reaching about the mid-seventies. Requires a good supply of microalgae and as with the above species, not suited for tropical aquariums but continue to show up in the trade.

Trochus Snail

More a warm water species, Trocus niloticus hails from the Tropical Western Pacific Ocean, Great Barrier Reef, Northern and Western Indian Ocean and inhabits shallow coastal areas. It has a temperature range of 72 to 83°F (22 – 28°C). Requires a good supply of microalgae. Well suited for tropical aquariums, however get quite large, about 6 inches (15 cm).

Family Turbinidae

This family probably contains the most useful of all snail species as they are widely used for keeping inside aquarium panels clean along with various substrates such as rock free of unwanted algae with no harm being done to other invertebrates. And must say I was probably the first hobbyists to utilize the Turbo species in aquaria, as I started bringing them back from trips to Mexico in the early 1980's. When I found them doing such a good job in controlling unwanted algae, I mention this to a person who owned a local aquarium shop. He began collecting them himself in Mexico and selling them as Turbo-Grazers. From there the use of snails in aquaria blossomed and now includes many other useful species.

Astraea Snails

There are several species all looking quite similar in the genus 'Astraea' with all being collected in the Western Atlantic Ocean, from North Carolina to the Caribbean. These excellent herbivores all tend to inhabit seagrass beds, mid-intertidal zones and rocks on upper reef areas. Some have common names such as American Turbo or Star Snail. The species A. tectum is the most popular of all snails amongst aquarium keepers as it's smaller than the turbo species described next and long lasting in aquaria. They are excellent algae grazers, especially brown diatom algae and green microalgae, yet won't harm decorative macroalgae, such as Caulerpa. Because of their small size, about 1 inch (2.5 cm), they are less apt to knock things over, yet more is needed with one per five gallons in average reef aquariums a good recommendation. Best of all, they are self-sufficient and need no special care or feeding and only seem to die-off if there is a lack of algae to eat. They often breed in aquaria, and supply what seems like an endless supply of these snails.

Turbo Snails

The species Turbo fluctuosus, also called the Turbo Grazer, Turban Snail, or Chevron Snail, hails from the Eastern Pacific Ocean and Western Atlantic Ocean: Sea of Cortez, Gulf of Mexico south to Peru, and inhabits intertidal zones where rocks are covered with algae. Its preferred temperature range is 68 to 79°F (20 – 26°C), and can attain a size of almost 4 inches (10 cm). Usually a greenish-brown with a brown and white chevron pattern along the spiral cords. Due to their somewhat large size, they can knock things over in the aquarium and cause possible damage to some invertebrate. Yet, they do provide good control for unwanted algae growths, but will not consume the longer hair algae strands. Unfortunately they appear to be weak shippers since they stress very easy and must have a constant supply of food. They are also mostly nocturnal feeders, yet will scavenge for food during daylight hours when very hungry. When they appear to easily loose their footing and continue to fall off rock and aquarium sides, they are extremely weak and should be removed from the aquarium before they die. One dead snail can quickly foul a small aquarium. Two snails per fifteen gallons is the usual stocking recommendation. There's also the 'Orange Turbo, Turbo heisei' that hails from the Western Atlantic, from Florida to Brazil, yet rarely seen in the trade.

Family Stomatellidae
Dove Snail

There are also other common names for this species, Stomatella varia, such as the Shell-less Snail or Slug Snail. It comes from Tropical Indo-Pacific where it inhabits shallow rocky coastlines, back reef areas, seagrass beds, and lagoons where microalgae exists. Most often imported as freebies on rock from Indonesia and Fiji. These small snails, about 1.0 inch (2.5 cm) generally feed upon microalgae and small particulate matter that coat various types of substrate by using a rasping motion of its mouthparts. Their colors vary, e.g., brown, brownish-green, tan, gray, black, or mottled, depending upon area of origin.

Its one of the more odd looking snails, as many mistake it for a nudibranch/slug. Even though many call it a "shell-less" snail, that is incorrect as it does have a small, flattened, cap-like shell on top of its body that is covered by flesh. If its general appearance was not odd enough, when disturbed it drops the rear portion/tail area of its body, similar to what some desert lizards do when frightened. And the detached portion twists and turns so as to attract the predator while the main body moves away at an amazingly fast speed!

Generally a nocturnal herbivore in the wild, yet specific diet information is still unknown. It seems to be quite safe in reef tanks and requires no special care, at least known at this time. Also seems to multiply quite quickly, however if the aquarium has predators such as shrimp or crabs (including hermits), its population may dwindle.

Family Architectonicidae
Box/Sundial Snail

This species, Heliacus areola is from the Indo-Pacific, and often arrives as a hitchhiker on zoanthid colonies. It has a flattened spiral-shaped shell that is checkerboard in color, e.g., somewhat black and white. Usually found feeding upon zoanthid colonies, however also feeds on soft and stony corals. Remove when seen!

Family Cerithiidae
Cerith/Tower Snails

Coming from both the Indo-Pacific and Western Atlantic these small tower-like snails inhabit shallow reefs and intertidal zones having ample supplies of microalgae. They are very good herbivores, especially for controlling diatoms and microalgae, however not filamentous algae. They also feed on detritus and help aerate the sandbed. Yet hermit crabs may attack them for their shells.

Family Cypraeidae

These are pretty snails, yet mostly carnivorous creatures and even the few herbivorous species tend to get too large for most aquariums. Most feed on corals, sponges, colonial anemones, and ascidians, e.g., Cypraea tigris.

Family Ovulidae
Flamingo Tongue

This species, Cyphoma gibbosum is closely related to cowries, and hails from the Western Atlantic Ocean: Florida, Bahamas to the West Indies. It has a temperature range of 72 to 79°F (22 – 26°C) and even though a very pretty mollusk that reaches about 3 inches (7.5 cm), unfortunately it's fond of eating gorgonian tissue/polyps. Has a cream-colored mantle with irregular yellow and tan spots edged in black. Totally unacceptable for use in reef aquaria.

Family Strombidae

There are two herbivores in the Genus Strombus that interest some aquarists and both hail from the Western Atlantic and inhabit turtle grass beds. One is called the Fighting Conch, S. alatus, and the other more popular S. gigas the Queen Conch. They both have a temperature range of 72 to 79°F (22 – 26°C), and are a glutinous consumer of algae and somewhat stir up the sandbed while hunting various foodstuffs. Small specimens are fine for the aquarium, especially one that is enduring an unwanted algae occurrence. Yet they get quite large quickly, about 10 - 12 inches (25 - 30 cm) within a year or two and can weigh about 5 pounds. Even a small 4 or 5 inch specimen would be too large for most hobbyist aquariums. However, while very small in size, e.g., 1 – 3 inches, it will eat algae off the surface of the sand and rocks and even the sides of the aquarium. But when getting slightly larger, will remain of the sandbed surface where it will be necessary to feed it algae pellets/algae-based foods to sustain it. And if not receiving sufficient food, might bury itself in the sandbed and die creating a large poor quality bulk water condition in the aquarium! Keep in mind this species grows quite quickly, as its full length can be attained within 5 – 7 years. And if not supplied with enough algae it will slowly starve to death. Only mariculture specimens are legally available in the trade.

Family Vermetidae
Tube Snail

Members in this family hail from the Indo-Pacific and live in worm-like tubes and do not move around like other snails. They secrete a slime that is trailed out into the water in order to catch suspended matter. Their tubes can exceed 10 inches (25 cm) in aquariums. Harmless and usually seen in reef aquariums with live rock. Often comes in attached to live rock. There's also a species that comes from the Atlantic Ocean. Also harmless, and requires no feeding.

Family Buccinidae
Bumble Bee Snail

Members in this family are called "Whelks" and most are predatory and have no use in reef or fish-only aquariums. This species, Pusiostoma (Engina) mendicaria hails from the Indo-Pacific Ocean: Japan, and east to Marshall Islands and is found in intertidal zones. Anthony Calfo and Bob Fenner in their book "Reef Invertebrates, An Essential Guide to Selection, Care and Compatibility" express an opinion that these snails do not serve much useful purpose in reef aquariums and they are physically unable to eat algae. They go further to say they are predatory snails feeding upon worms and possibly other desirable fauna. Personally, see little value except for a nice looking small snail that might be interesting to watch.

Family Conidae
Cone Snails

Those in this family with the genus name 'Conus' are cone-shaped and are carnivorous and venomous creatures, and must be handled with extreme care, or preferably not handled at all! They are found in both in the Indo-Pacific and Eastern Pacific, and feed on a variety of bottom dwelling animals including worms, clams, other snails, and resting fishes, e.g., Conus marmoreus, the Houndtooth Cone Snail. Beware!

Family Eulimidae
Blue Linckia Snail

This family contains a parasitic snail, Thyca crystallina that infests the Sea Star species Linckia laevigata, or what is generally called the Blue Linckia starfish. These starfish should be thoroughly inspected for this parasite before placing it in the aquarium as any feeding wounds can develop secondary bacterial infections/loss of the starfish.

Family Fasciolariidae
Tulip Snails

This is a family of carnivorous snails that feed upon worms, small fishes, clams, and/or dead organic matter. Species in two genera occasionally show up in the trade, with the first Fasciolaria tulipa from the Caribbean called the Tulip or Caribbean Whelk Snail. The second, Opeatostoma pseudodon, is called the Thorn/Banded Tooth Latirus, which hails from Central America: Baja California to Peru and the Galapagos Islands. Both are not suitable for most aquaria as they prey on other gastropods, such as clams. They are burrowing type snails and may be fitting in fish-only aquariums with a deep sandbed, yet not suited for reef aquaria.

Family Muricidae
Murex Snails

There are various genera in this family, all having ornate shells, which is the reason many are collected. They are found in the Pacific and Atlantic Oceans, however are not suited for reef aquariums as they are capable of boring into other shell-protected animals such as Tridacnid clams. In other words they are snails that eat other snails and clams. They do so by secreting an acid that dissolves the calcium carbonate of the protecting shell and then consume the soft tissue inside. The species Chicoreus ramasus is a good example.

Family Nassariidae

These small "Whelk" snails, about 0.5 inch (1 cm) live buried in sand and emerge to eat foods high in protein, such as excess meaty fish foods and/or dead or dying animals. They do not consume algae and should not exceed a few per square foot of sandbed surface. Also, they should not be kept in aquariums with hermit crabs, as hermits may eat them.

Mud Snails

The genus Nassarius contains an often seen in the trade species, N arcularius, simply called the 'Mud Snail.' It hails from the Tropical Indo-Pacific and inhabits intertidal areas where mud and/or organics accumulate. These snails are extremely good scavengers and usually reside buried in the sand, which they plow through like a snowplow going through a snowdrift, and feeding upon found detritus. They are somewhat small, 18 – 40 mm, and when the aquarium is fed, emerge from the sand and begin to cruise the aquarium looking for uneaten foodstuffs. They have a large foot area that helps them quickly glide over substrates of various sizes and a long trunk-like projection called a 'proboscis,' which is used similar to that of a direction finder to help locate uneaten meaty foods. They are quite safe, as I've had them in my aquariums and have never seen any living creatures harmed by their travel over them. Chances are they will rarely be seen unless the aquarium is overfed with meaty foods. But they are relentless workers, helping to reduce accumulating detritus in the sandbed and doing away with uneaten meaty foodstuffs.

They also don't appear to need any special care or feeding, as they simply 'pop-up' from the sand and 'charge' with their proboscis waving wildly in the water towards any uneaten food that remains in the aquarium. Fun to watch!

It's my understanding these snails are not overly abundant in the trade, and what is seen are mostly coming from the Philippines. Because they appear to be collected in shallow muddy pools or tidepools it would seem logical that they are accustom to salinities more in the range 1.025 or slightly higher. Other water quality issues such as excessive nitrate and phosphate levels would not be an issue since they come from areas high in organics. And since they are already accustom to higher salinity levels, recommend acclimating them carefully to your aquarium water conditions before adding them to the aquarium.

Sea Hares

Family Aplysiidae
Spotted Sea Hare

Sea hares live in shallow coastal waters where algae cover much of the substrate. They are an excellent herbivore, yet it is said they have a short life span of about one year. There are both cool water and tropical species; however, the species Aplysia californica, called the Spotted Sea Hare from the Eastern Pacific Ocean is often seen in the trade. It inhabits seaweed and seagrass areas, and has a temperature range of 65 to 78°F (18 – 25°C). It feeds on algae of all types and may reach a length of 12 inches (30 cm) or larger. It's a valuable herbivore for algae infested aquariums, but can also expel an ink cloud when disturbed; yet it's harmless to fishes.

Sea Slugs

Family Elysiidae

Members of this order are highly specialized plant consumers and they are usually less than 3 inches (7 cm) in length. Of special interest is one member because it is generally available and has become known as a major algae consumer.

Florida Lettuce Slug

There remains some discussion on its genus, and whether or not its Elysia crispata or Tridachia crispate, nevertheless, it hails from the Western Atlantic and is found on green seaweed's and in seagrass beds in intertidal zones. It has grown popular because of its fondness for hair algae, such as Bryopsis. Caulerpa may be a good food source when other green algae become less available.


This is the most physically diverse subclass of gastropods with over 3000 known species. The name nudibranch means naked gills since their feather-like gills are generally exposed along their dorsal area. However some species, e.g., Phyllidiids, have its gills beneath the mantle. Some species can increase their gaseous exchange by ruffling the mantle edge or through small projections called cerata, which contain stinging nematocysts derived from their diet.

They are simultaneous hermaphrodites, meaning they are both functionally male and females at the same time. Nevertheless they cannot self-fertilize and thus need a partner. When mating they play both male and female roles, so both specimens can lay eggs thereafter. In fact, the sperm can be stored for use later and the eggs laid are usually embedded in a coil-shaped mucus net that is adhered to a hard surface - when the mood arrives.

These small creatures have caught the interest of some marine hobbyists because of their exquisite colors, which actually serve as a warning to predators. Mostly small, less than 3 inches (7 cm), these snails without a shell are all carnivorous. In the aquarium their natural food source is mostly in short supply, limiting their life span considerably. In fact, lifespan of most nudibranchs is less than one year from time of hatching. Fish won't eat them as they have a strong acid gland that makes them taste terrible. Since they are basically predatory animals, they often find anemones, gorgonian, hydroids, tunicates and sponges a delicacy.

And since its almost impossible to judge their food needs, they often perish in aquaria and this poses a serious health risk to the other inhabitants in the same system. Since most are toxic and short lived in captivity, it simply does not make sense unless you're fully aware of the specimen's needs, to house it in your aquarium.

The taxonomy of the Suborder Nudibranchia is still under investigation, but for the sake of simplicity here I'll subdivide it into four Superfamilies.

Doridoidea - those having the most common species known to aquarists. These "Dorid" nudibranchs were named after the sea goddess Doris in mythology. They have a pair of tentacles near the top of the head and several feathery gills near the rear section. Their members feed upon specific sponges, barnacles, sea squirts, soft corals, hydrozoans, hydroids and bryozoans and/or release toxic chemicals fatal to shrimp and fishes.

Aeolidioidea – those who are almost completely covered with finger-like appendages (tubercular nudibranchs). Their common name of 'Aeolids' was named after the god of wind "Aeolis." They can withdraw their gills into their body as a defensive tactic. They seem to prefer soft corals and gorgonians.

Arminoidea – these 'veiled nudibranchs' have an expanded fleshy lobe on their head and ridges running longitudinally along the length of their dorsal area and feed upon sea pens.

Dendronotoidea – these side-gilled nudibranchs have a cup-like sheath surrounding each top head tentacle and feathery gills along each side of their back. Its members are known to eat soft corals such as Sarcophyton, Sinularia, and Cladiella and gorgonians.

There is one species of special interest in the Doridoidea that is worth mentioning.

Family Scyllaeidae
Aiptasia Eating Nudibranch

This species, Berghia verrucicornis hails from the Western Atlantic: North Carolina to Brazil, Mediterranean Sea and West Africa and is found in shallow reefs near and on anemones, barnacles, sea squirts, soft corals, and sponges. It has a temperature range of 72 to 79°F (22 – 26°C). In fact, this may or may not belong in this Family, as information on this species is extremely slim. Yet, this small, about .5 inch (1 cm) nudibranch has become popular in the trade because it eats these pest anemones.

Class Cephalopoda - Octopuses, Squids, Cuttlefish and Nautilus

Since there is little interest in maintaining squid or cuttlefish in hobbyist aquariums, those will not be discussed here. Yet, if wanting information on these animals, suggest searching the web, as articles on their care are available.

As for octopus, they are found in both temperate and tropical oceans. Many have a short life span, usually less than two years and only mate once, then die, with the male dying shortly after depositing his sperm into the mantle cavity of the female. The female is capable of storing the sperm for a few months, but after depositing the fertilized eggs and caring for them until they hatch, the female then also dies.

They have the most well developed eyes of any aquatic invertebrate and even though they cannot hear, they have an excellent sense of touch and smell. They crawl and swim by drawing water into the mantle cavity and forcibly expelling it through their siphon tube. Similar to how a jet engine works. And they are also excellent at changing skin color as a means of a passive defense. At time of real danger, they eject an inky secretion that forms a dark cloud allowing for escape.

As for strength, they are extremely strong for their size. A small 5 inch (12 cm) octopus could lift an aquarium cover that is weighted down with a brick! Then crawl out and wander around your home! I know – been there, done that! Therefore, a secure escape proof cover is a must!

The ones I've maintained appeared to be quite ammonia sensitive and required very good water quality and excellent water movement, as they are also sensitive to low dissolved oxygen levels. Therefore a quality protein skimmer will be quite helpful, as would sufficient activated carbon, possibly placed in a canister filter along with phosphate removing media. They also like to hide during the day since they are nocturnal creatures, so provide sufficient caves/hiding places. Also, never place powerheads in the aquarium as they are inquisitive and will no doubt place their arm tips into the opening that house the impeller causing them damage. Don't forget to give them enough 'toys' such as PVC elbows, corral rubble of different sizes, open glass bottles, etc., to move around and investigate. And if there is an occasion where the species inks for some reason such as being threatened or stressed, perform a partial water change as soon as possible. For tropical species maintain a temperature range of 76 – 80°F degrees. All in all they are highly intelligent and make good, but short-term pets, yet are best kept by themselves unless you can obtain a heterosexual pair.

And while these creatures are highly interesting and fascinating to watch, they do have special care requirements that must be met if they are to survive. If not willing to or able to provide their needs, its best to keep less demanding species!

Family Octopodidae
Blue Ringed Octopus

Those in the genus Hapalochlaena hail from the Indo-Pacific and are found in shallow reef areas and under stones and rock during the day. They hunt in evening hours. H. lunulata is one of about five known species in this genus, which feed mainly on small crustaceans, but will also consume small fishes and crabs. It has a body diameter of about 1 inch (2.5 cm) and the bite from this creature can easily kill a human in 15 minutes or less. In captivity they should be fed every other day, preferably small pieces of fish or shrimp flesh, and if possible, some small live hermit crabs or snails when available. Extreme care is advised if you decide to maintain one of these creatures! And even though I've seen friends maintain them, I was never comfortable for their safety knowing they had one of these creatures in their home!

Two-Spotted Octopus

This is my personal favorite, as I've captured a couple of these over the past few decades while in Mexico waters. This species, Octopus bimaculatus is found throughout the eastern Pacific from California to Mexico and inhabits intertidal zones. In fact, that's exactly where I would find them in early morning hours by simply turning over rocks in the intertidal areas. It has a temperature range of 65 to 75°F (18 – 24°C) and feeds mainly on crabs and clams, but will also consume fish and shrimp meat. Has a main body diameter of about 6 inches (15 cm).

Had a friend that built a large glass aquarium to hold this species and while having one in his tank, it lifted the weighted down tank cover one night and was found dead the following morning in the kitchen in front of the refrigerator. The joke thereafter was that it could not reach the refrigeration door handle for a midnight snack and died of starvation! A true but sad story!

Family Nautilidae
Nautilus/Chambered Nautilus

This strange snail-like animal, about 8 inches (20 cm), is a relative of the octopus, cuttlefish, and squid. It has changed little over the past 500 million years and is considered by some to be a living fossil. Nautilus belauensis, N. macromphalus, N. pompilius and N. stenomphalus are among the known existing species. It's a deep living species, capable of migrating from about 1500 feet (450 m) to approximately fairly shallow waters at about 300 feet (90 m) without internal damage or being affected by temperature changes. This seems to occur daily when they feed upon shrimps, crabs and other small invertebrates during evening hours. When viewed from the top, the shell is dark with irregular stripes, making it blend into the darkness of deeper water below it. Viewed from below, the shell is white, therefore blending with brighter water above it. This form of camouflage is called 'countershading.'

As the animal grows, its body moves forward and a wall called a 'septum' seals off the older chambers, which is why it's called a 'chambered' nautilus. In fact, its shell is divided into a various number of compartments depending upon its age – about 4 as a newly hatched specimen and about 30 compartments in an adult stage. As it ages, its body moves to the outer compartment, leaving the most inner areas/compartments vacant except for a gas, an argon-nitrogen mixture, in the older closed chambers that is used to control its buoyancy. A tube that connects the older gas filled chambers allows it to adjust its height in the water by manipulating the ratio of liquid gas and seawater in those chambers, thereby changing its weight/ballast, similar to that of a submarine. It moves by pulling water into its mantel cavity and forcing it out, similar to how octopus move. The direction the water is forced out controls the direction of its movement, which can either be forward, backwards or sideways.

Its eyes are poorly developed, and its best to maintain these creatures in a somewhat darken environment. Diet consists mainly of small fishes, crabs, and shrimp. I know of only one hobbyist many years ago that successfully maintained several nautiluses. He did so in a large Hex-shaped tank and kept the tank somewhat shaded during the day when he was at work. Upon getting home, a small fluorescent lamp was lit above the tank. It was thought this would signaled feeding time, yet as time passed it seems these animals had a keen sense of smell and by placing some food in the water they would slowly rise to the top of the water where they were handfed pieces of shrimp and fish flesh. Their small tentacles, up to ninety per specimen, do not have suckers such as what octopus have, but do have grooves and ridges that are capable of gripping food items. Since they waste little energy in captivity, it was said they only required feeding once per month.

The goal of the above mention hobbyist was to breed this species, however, lost contact with him before he succeeded. Nevertheless, it takes about 5 years for the nautilus to reach sexual maturity, and similar to cuttlefish and octopus, the male uses its tentacles to hold the female while a modified arm transfers a sperm package to the female's mantle cavity. The female then attaches one leathery covered egg to a hard surface where it remains for about 8 – 12 months before a baby nautilus of about 1 inch (2.5 cm) emerges already having 4 chambers to control its buoyancy. Adults can live for 10 – 20 years. Not an animal for the beginner unless thoroughly researched and provided adequate surroundings, at least a high 100-gallon tank that is dimly lit, and hand fed as required.

And let me thank and for some of the above information, as I've had no personal experience with this interesting creature.

Phylum Echinodermata

This Phylum contains over 6,000 species in 6 Classes having 35 Orders. The word echinoderm means 'spiny skin' and this Phylum includes urchins, brittle stars, starfish (Sea Stars), cucumbers, and feather stars. These creatures have an internal calcium skeleton and travel using tube feet. Their vascular system pumps water, not blood. By pumping water into or out of their tube feet, the animal is capable of securing itself to most surfaces. Their mouth area usually contacts the substrate, except for cucumbers. They are scavengers and/or filter/suspension feeders.

Class Crinoidea - Sea Lilies/Feather Stars

Feather Stars are members of the Order Comatulida, and Sea Lilies members of the Order Isocrinida, with both forming the Class Crinoidea. There are about 400 species of feather stars, and like basket stars, they are extremely attractive.

Both sea lilies and feather stars are attached by a stem to the seabed floor, however feather stars break free for their adult life and become capable of swimming to where the food supply suits them. The stalked sea lilies, which are very rare, are confined to deeper waters and rarely ever seen in the trade therefore they are not included here.

These creatures lack eyes and can contain between 10 to 200 arms attached to a central disk called the calyx. Each arm can also have lateral branches, hence their common name. Even though they have tube feet, they do not use them for locomotion, instead they use claw-like appendages called 'cirri' for grasping the substrate. They are capable of moving through the water column when threatened or dissatisfied with their location by alternating the movement of their arms.

They are suspension feeders and uncoil/coil their arms to gather only extremely fine planktonic food. They also require very specific water currents in the course of gathering food. Without specific attention to their needs, they slowly digest themselves and disintegrate. Usually active at night these Crinoids are better left in the ocean, as they are quite difficult to maintain in aquaria.

Family Comasteridae
Schlegel's/Black & Gold Feather Star

Unfortunately I've seen this species, Comanthina schlegelii show up in the trade several times. It hails from the Indo-Pacific and inhabits coral reef areas rich in corals, gorgonians and coral rubble. It has a temperature range of 72 to 79°F (22 – 26°C) and these suspension feeders uncoil or coil their arms to gather extremely fine planktonic food and/or provide locomotion to swim to other areas. And as mentioned above, they requires very specific water currents in the course of gathering food, and without exacting and very specific attention to their needs they slowly digest themselves and disintegrate. Truly, they are better left in the wild

Class Asteroidea - Starfish/Sea Stars

The word starfish is a misnomer as these are of course invertebrate, not fish. However their star-shaped body lends certain realism to the term. True starfish comprise the Class Asteroidea and there are about 1600 species, with only a few truly suited for the aquarium. They can be found to depths of 20,000 feet and the majority of starfishes now more properly referred to as sea stars, are carnivorous or omnivorous and can eat small fishes, algae, mollusks and coral polyps. In fact, they don't have to fit their prey into their mouth as they are capable of expelling their stomach and digesting whatever they are resting upon, such as what the Crown-of-Thorns does to coral polyps.

These creatures have an internal calcium skeleton and travel using tube feet. Their vascular system pumps water, not blood. By pumping water into or out of their tube feet the animal is capable of securing itself to most surfaces. Their mouth area contacts the substrate, except for cucumbers. And except for cucumbers, have no anus and waste exits the same opening. They also have the ability to regenerate an arm if lost. In fact, most of their organs are repeated along their arms and if part of the central disc is attached to the severed arm a whole new sea star can be generated.

Mostly nocturnal, these bottom dwelling multi-arm echinoderms are excellent scavengers and some of those mentioned below are extremely easy to maintain, yet some are not recommended for reef systems. A good rule of thumb for reef keepers is to avoid any starfish with knobby backs such as those in the genus Protoreaster. And keep in mind; all starfish are very vulnerable to sudden salinity changes.

Family Astropectinidae
Sand Sifting Star

There is only one species of interest here, one that is often called the 'Sand Sifting' starfish, and that is Astropecten polycanthus. It hails from the Indo-Pacific and is found in the upper levels of sand in protected lagoons. It attains a diameter of about 5 inches, (12.5 cm) tip-to-tip and it's a 'predator' of other buried invertebrate. They will turn over the sandbed, however, will eat all valuable sandbed invertebrate!

Family Asterinidae
Fiji Star

This small star, less than 1 inch (2 cm), Asterina anomala, hails from the Indo-Pacific and inhabits areas of heavy coral growth in shallow coastal areas. They seem to arrive on live rock and coral specimens. It's a predatory star that eats sps, soft coral, and coralline algae. They are large bodied with short arms and sometimes visible where aquarium side panels meet the substrate when the lights dim and/or hide under corals during day. They divide across the main body with two or three legs of various lengths. Even though there is some thought there might be 'safe' similar looking members in this family, recommend removing these stars as they quickly multiply! It is said the Harlequin shrimp Hymenocera elegans will consume them.

Family Ophidiasteridae

There are still many undescribed species in this family, and to make it even more difficult to tell some of them apart, their colors and color patterns change with age and/or environmental conditions. Yet they all appear to be reef safe and good scavengers of detritus, microalgae, small benthic invertebrates and other organic matter.


There are several in this genus that are frequently available in the trade, e.g., F. elegans the Red Star; Fromia ghardaquana the Ghardaqa Brittle Star; F. indica the Indian Brittle Star; F. milleporella also called the Red Star; and, Fromia nodosa the Knotted brittle star to mention some. All very good choices for the reef aquarium.

Icon Star

The species Iconaster longimanus hails from the Indo-West Pacific, and is usually found in deep reef areas where rubble collects. Even though its diet in the wild is still unknown, its thought to feed upon detritus and small benthic invertebrates. This is a very pretty sea star which has five thin, flattened arms with its marginal plate areas usually having large light tan and dark brown plates that surround the smaller central disk plates of burnt orange. Overall colors vary slightly depending upon where in the wild it's collected. Rarely seen in the trade and appear to be reef safe/good scavengers, yet long term success with these animals is quote poor, but placing different type and size organic foodstuffs on the aquarium substrate just prior to the lights going out may be way to lengthen their stay in aquaria.

Blue Star

There are a few species in the genus Linckia, with the most popular and most often seen L. laevigata, sometimes called the Blue Linckia, a favorite amongst many reef keepers. It hails from Eastern Africa to Hawaii, the South Pacific Islands, and Japan, and inhabits lagoons and outer reefs on all kinds of substrates. Fully grown its about 12 inches (30 cm) tip to tip and their suitability for the reef aquarium is sometimes questionable because they are prone to the infestation of small burrowing bivalves and parasitic snails (Thyca crystallina), and also secondary bacteria infections. Yet, once successfully acclimated, seem to do fairly well in aquaria. They are basically herbivorous and detritus feeders. Occasional feedings with algae pellets may prove beneficial. They are capable of regeneration and reproduction by fission as entire new stars can be reproduced from a single removed arm.

Family Oreasteridae
Chocolate Chip Sea Star

There are two in the genus Protoreaster, that of P. lincki the Red knobbed Star, and P. nodosus the above named star that should be avoided in reef aquariums. They hail from the Indo-Pacific to Eastern Africa and are found on shallow sandy and muddy bottoms, and in seagrass beds and back reef areas where it is thought to feed upon sponges, anemones and other benthic invertebrate, even sleeping fish! They are not suited for reef aquariums!

Its usually available in the trade simply because its plentiful and easy to catch in the wild. As to its nutrition, because of its bulky size, i.e., wide arms and thick spiny body, it is usually incapable of searching areas between close-fitting rocks, therefore must traverse the more wide open sandbed surface limiting its food intake. Therefore, as with the Icon species described above, suggest placing different organic foodstuffs on the aquarium substrate just prior to the lights going out. Most die of malnutrition in aquariums.

Class Ophiuroidea - Brittle Stars

Sometimes referred to as serpent stars and contains approximately 2000 species. Like starfish/sea stars, they have five arms radiating outwards from the central area. They differ only in that their arms are very thin and flexible. They prefer to hide under rocks during the day and search the bottom during nighttime to feed on organic matter/detritus. Even though most are not colorful, they are an excellent addition to well-established reef aquariums, especially those containing a well-established sandbed.

They have the same regenerative capabilities as do sea stars and can regenerate lost limbs. They differ from sea stars in that their tube feet serve a respiratory purpose only, not for locomotion purposes as they do with sea stars. Also, brittle stars only have a mouth, whereas starfish have both a mouth (on the bottom) and an anus on top.

Smooth armed species are usually referred to as serpent stars and those with spiny arms as brittle stars.

Family Ophiodermatidae
Brittle Stars

There are several in this family that show up in the trade and make good additions. From the Indo-Pacific the green brittle star Ophiarachna incrassata is probably best known and frequently available. From tip to tip its about 22 inches (55 cm) in the wild and feeds upon organic matter/detritus. It has short yellow and black bristles along its green arms, and the only drawback is that it may eat small fish and shrimp.

Another in this family, Ophioderma appressum and called the Banded Brittle Star, Harleguin Brittle Star or Zebra Brittle Star hails from the Caribbean. It reaches a 5-inch (13 cm) diameter and often has yellowish-white and dark green bands along its arms and a pentagonal star on the upper surface of its main body.

A third in this family is Ophioderma squamosissimum, also coming from the Caribbean. This bright red brittle star is the largest found in this area at 8 inches (20 cm). All of the above are suitable for reef or fish-only aquariums.

Class Echinoidea - Urchins

Urchins, Greek for 'like a hedgehog' are sphere-shaped, multi-spine nocturnal creatures that are excellent herbivores. There's probably over 900 described species coming from shallow to areas several miles deep. They also feed on detritus, dead animals or are simply filter feeders. Those preferred by marine hobbyists often feed on algae, including the preferred coralline algae. In fact, urchins have a desire for calcium carbonate and can be given pieces of cuttlebone to graze upon, which may help satisfy this need and possibly save some of your valuable coralline algae.

Between their spines are tube feet and small pincer-like organs called 'pedicellariae' that is used to clean and defend themselves, some of which contain poison glands. Both spines and tube feet help move them, and their mouths always face the substrate. They are also rather clumsy and may knock over anything smaller and possibly slightly larger, which isn't secured. Beware; even though some are great alga consumers, they can be bulldozers! And do not purchase a specimen that is losing its spines, as this may be a sign of poor nutrition and/or shipping damage that may be impossible to overcome.

Family Cidaridae
Pencil/Mine Urchin

The species Eucidaris tribuloides hails from the Western Atlantic and the Caribbean and is commonly available in the trade. Its central body, called a 'test' reaches about 2 inches (5 cm) and its primary spines are arranged vertically in rows of ten. The secondary spines are also in rows of ten and are reddish brown to tan. It a hardy long-lived species and feeds upon algae, including coralline, detritus, and encrusting invertebrates. Caution, it's a bulldozer.

Family Diadematidae

There are several in this long-spined urchin family that appear quite frequently in the trade. Most of the five species have hollow spines containing a venomous surface skin that can cause a burning sensation if it punctures 'your' skin. Since their spines, which have reversed barbs is very fragile and easily broken, they are difficult to remove once your skin has been penetrated and can cause pain and swelling. Seek medical attention is my advice should you get stuck by either of the follow two species!

Hatpin/Black Long-spined Urchin

This species, Diadema setosum, hails from the Indo-West Pacific/Red Sea to South Pacific and north to Japan and gets quite large, about 12 inches (30 cm) in diameter from spine tip to opposite spin tip. Unlike a similar species, D. savignyi, which has a bright blue star pattern on its test, it has numerous tiny blue spots near the margin and five large white spots in a pentagonal arrangement around the anus. And in most specimens there's an orange ring around the anus. In some cases the spines are white banded in some juveniles, with them being a solid black in adults. Basically a nocturnal creature and consumes huge amounts of algae. Needs wide-open spaces in the aquarium to traverse because of its long spines.

Double-spined/Hatpin Urchin

The species Echinothrix calamaris hails from the Indo-West Pacific and is about half the size of the above species, with brown secondary spines bunched together under the primary longer white-banded spines. It has the same diet needs, i.e., lots of green algae, and is also poisonous, so handle with much care.

Family Strongylocentrotidae
Purple Urchin

There are two in the genus Strongylocentrotus with the same common name that occasionally show up in the trade, S. purpuratus and S. franciscanus, and both hail from the East and West Coast of the United States, and the Gulf of California. Both inhabits intertidal zones and have a temperature range of 59 to 68°F (15 – 20°C). The first has a body size about 3 inches (8 cm) with short spines, and the second attains a maximum of 7 inches (18 cm) in diameter with spines reaching up to 3 inches (8 cm) long. The second is somewhat more reddish in coloration and are sometimes called Red Urchins and may reach a lifespan of 30 years. Both have their eggs used in sushi bars. They consume huge amounts of algae and are nocturnal as are most urchins. They do not fare well when water temperature nears the high seventies. Those in the foreground of this photo are S. purpuratus and those in the background are S. franciscanus.

Family Temnopleuridae

The urchins in this family and the following are more 'globe' shaped with short spines, which are used more for locomotion than defense. All in these families will eat algae 'and' encrusting invertebrates.

Blue Tuxedo Urchin

This species, Mespilia globules, hails from the Eastern Indian Ocean to Western Pacific and inhabit reef terraces, beneath overhangs, crevices and also found on rock and rubble areas covered in algae. Its body/test has five spineless zones which are velvet green or blue. Between these zones is short spines reddish-brown in color. It is extremely hardy and a good algae consumer.

Salt & Pepper Urchin

This species, Salmacis dussemieri, hails from the Indo-Pacific and Red Sea and inhabits rock and rubble areas covered in algae, including seagrass beds. It may have other common names, but because of its color this name fits it nicely. Also globe-shaped and nocturnal with short spines and attains a spine tip to spine tip diameter of about 3 inches (7.5 cm). A very good algae and coralline consumer.

Family Toxopneustidae

Some of those in this family are toxic, as is the species discussed below which is commonly imported.

Priest-Hat Urchin

This species, Tripneustes gratilla, hails from the Indo-Pacific and Red Sea to Hawaii and inhabits reef rock and rubble areas covered in algae. Often called the Sea Egg, Halloween or Collector sea urchin because its colors vary greatly - from having white to orange colored spines having a velvet-like zones between the spines that can be many different colors, e.g., white, red or bluish. In the wild it browses on seagrass and macroalgae and in the aquarium will eat large amounts of algae very quickly. However, the small appendages on its test, i.e., pedicellariae, contain a toxin that can cause painful stings. It is wise not to handle this species. Since it's a large algae consumer and very hardy it makes it way into the trade, but it also consumes soft corals so not something for many reef aquariums.

Class Holothurioidea - Sea Cucumbers

These are gentle unassuming creatures that mostly look like a shriveled-up old cucumber, hence the name. Even though they are the most common animals found in deep ocean environments, most well known species and/or aquarium specimens come from shallow reef and coastal areas. They range in length from less than 1 inch (2.5 cm) to more than 3 feet (one meter). Some burrow into the substrate and feed by spreading mucus-covered tentacles into the water column to collect suspended matter. Others spend their time gliding over sand and rubble looking for pockets of detritus and/or diatom-coated sand grains, or filter-feeding on planktonic material such as the Sea Apple (Pseudocolochirus).

There are also worm-like cucumbers called Medusa worms. These legless sea cucumbers are members of the family Synaptidae (Order: Apodida). They all look quite similar with soft and flaccid bodies with rounded knobs. They project their tentacles directly into the substrate to collect organic coated particles, and are relatively nontoxic when compared to other cukes, especially the Sea Apple. The most common genera are Euapta, Synapta and Synaptula from the Indo-Pacific. Those from the Caribbean are usually Euapta lappa or Synaptula hydriformis.

Many of these creatures are nocturnal and all require large amounts of foodstuffs which they process fully within about one hour. For some species, sinking shrimp pellets are a good food source should there not be enough detritus coated material in the aquarium. And it's not a good practice to place any of the roaming sand and rubble cleaners in newly established aquariums, as they will quickly starve. And be forewarned, cucumbers will grow smaller if they don't find sufficient food. If this happens or they are pestered by tankmates, they should be removed from the aquarium before they release deadly toxins (holothurin and holotoxin). Even though happenings such as this is quite rare, these toxins, chemically called triterpenglycosides, will cause fishes in the aquarium to act skittish, exhibit respiratory distress and probably die soon after exposure. Other invertebrates are usually not effected. Since these toxins reduce water surface tension, a protein skimmer may overflow. And if a cucumber is sucked into a powerhead and shredded, recommend a major water change, increased protein skimming and possibly a canister filter with an ample amount of activated carbon be quickly employed.

Even though most are fairly ugly, some are excellent substrate cleaners, such as some members in the genus Holothuria, e.g., H. hilla, H. impatiens and H. thomasi. Sand and organic material that go into one end are separated, with organic matter being digested and sand particles expelled at its opposite end. Always reminds me of something like a car wash!

Family Cucumariidae

The members of this family are suspension feeders and require frequent feedings with plankton-like foodstuffs. If stressed, they can release a toxin capable of killing fishes, not other invertebrates

Yellow Cucumber

This species, Colochirus robustus, hailing from the Western Indian Ocean to Japan is frequently seen in the trade. It inhabits shallow rocky reef and lagoon areas and gets to about 4 inches (10 cm) in length. Its a plankton feeder and spends most of its time on rocks filtering the current flowing past it. In aquaria it requires daily feedings with plankton-like foodstuffs, yet does fairly well in captivity. Remember, its not a sand stirrer and frequently reproduces in aquaria by fission (splitting in two). Has a temperature range of 72 to 83°F (22 – 28°C).

Sea Apples

Those in the genus 'Pseudocolochirus' are called Sea Apples and there are several species of interest, P. axiologus; P. tricolor; and P. violaceus, with the last frequently seen in the trade. They are a beautiful somewhat anemone-shaped cucumber and has rows of tube feet along the vertical length of the body. Its head area has a ring of feathery tentacles which it uses for collecting phytoplankton. They range in size up to about 6 inches (15 cm) and when they find a spot to their liking may remain there for years. Keep in mind they are filter feeders, not sand stirrers, as they spend most of their time on rocks or aquarium side panels. If it grows smaller it is starving and may die. Since they are capable of releasing toxic mucus when stressed by lack of food, tankmates, poor or excess current, etc, it's very possible it will kill fish, although probably not other invertebrates. Therefore it's safer to remove specimens that are becoming smaller or stressed. Needs daily feedings with phytoplankton products and has a temperature range of 72 to 83°F (22 – 28°C).

Family Holothuriidae

Members in this family are among the most collected because they are good sand shifters and quite hardy.


There are many in this genus that make it into the trade and first and foremost the Red Tiger-tail Sea Cucumber, H. hilla from the Indo-Pacific is an excellent sand-sifter. Hardy and often subdivides in aquaria. The species H. impatiens, the Mottled Sea Cucumber from the Indo-Pacific and Atlantic is another good choice. It can attain 14 inches in length (35 cm) in the wild. The species H. floridana from the Western Atlantic, Caribbean and Gulf of Mexico is another good choice. The so-called 'Edible Cucumber' H. edulis, from the Indo-Pacific and Red Sea is another good sand shifter, as is the Black Cucumber H. atra, also from the same areas.

Spiny Pink Sea Cucumber

The species Pentacta anceps often shows up in the trade as its an attractive creature. It hails from the Eastern Indo-Pacific Ocean, South Sea Islands, and Indo-Australian Archipelago and inhabits nutrient rich back reef areas. This small, about 4 inches (10 cm) cucumber is a suspension-feeder, getting its nutrition in a similar way as do sea apples. Does better in nutrient rich environments, with the addition of various brand phytoplankton additives very helpful in maintaining its health.

Family Stichopodidae

Members in this family are also good detritus scavengers, however if very stressed they have the ability to "melt" becoming totally limp and eventually disintegrating. Yet, they also have the ability to make surprising comebacks from what looks like sure death.

Black/Geenfish Cucumber

This species, Stichopus chloronotus hails from Indo-West Pacific: Eastern Africa to Hawaii and inhabits current swept sandy and rocky inner and outer reef bottom areas. It makes its way into the trade occasionally and can reach a length of about 12 inches (30 cm). It feeds on detritus and organic matter that is sifted from the substrate, and as with all cucumbers it wise to nail their family and genus, then do your homework as to its needs before placing it in your aquarium.

Family Synaptidae

Known as Sticky Worm Cucumbers or Medusa Worms, these creatures lack obvious tube feet and are sometimes called "legless" cucumbers. They also gain their oxygen and dispel carbon dioxide across the body surface. Often referred to as non-toxic cukes because they don't have the same defensive mechanisms as other cucumbers. These cucumbers are mostly specialized feeders, with detritus the main source of nutrition and/or in some cases the organic film that forms on sponges. Generally, they usually perish within a few months in most aquaria as they cannot get a sufficient amount of food.

Red-ring Worm Cucumber

This species, Opheodesoma spectabilis, hails from the Indo-Pacific to Eastern Africa and inhabits sandy reef bottoms. These long, 32 inch (80 cm) tube-like/worm-like cukes are an organic particle sifter and more nocturnal as it will generally hide under rocks during daytime. Probably best left in the wild.

Phylum Porifera - Sponges

These are the simplest of multicellular creatures. There are 3 classes, over 100 families, and probably over 10,000 species. Most are found in marine waters and vary in size, shape, and color. They are sessile filter feeders and posses no nervous, digestive or excretory systems and feed by filtering suspended bacteria and fine detritus. In fact, for hundreds of years they were considered plants, not animals.

The word 'Porifera' means pore-bearer and even though these animals are multicellular, those cells are uncoordinated and function individually, yet form large colonies and are found attached to hard substrates. They have a water current system that allows water to pass through internal channels so oxygen can be utilized, and in addition filter out food. Those currents are developed inside the sponge with beating whip-like hairs or flagella that are located on inside body walls and draw water in through numerous pore openings. Water and waste products are then expelled though other openings.

Strong water movement is vital to all species for carrying food to these sessile, non-photosynthetic filter-feeding animals and carrying their waste and unused matter away. In fact, a sponge the size of a baseball can filter fifty gallons of water per hour! Keep in mind almost all do best only in low light areas and where currents are quite swift.

Each sponge has both female and male reproduction capabilities. Cutting a piece from the healthy tissue and simply relocating it to another area can form new colonies. Newly purchased specimens should not be exposed to air during their trip home to your aquarium as air trapped in the sponge may kill it. New purchases should be bagged under water with no oxygen added or should the bag contain an air space while being transported. Sponges are not too sensitive to temperature changes, yet sudden changes in salinity may have drastic effects, therefore acclimate carefully.

New specimens should not contain any gray or white tissue, which is generally a sign of dying or dead tissue. However, it is possible to cut that section out without doing them harm, and of course this should take place under water. Sponges should be placed in shaded areas (PAR <100) where water movement is very good and detritus or algae do not accumulate on their surfaces. Since they constantly feed upon plankton and suspended detritus in the wild, numerous feedings per day of live and/or preserved commercial phytoplankton products or that of animal and plant powders that produce suspended products in the bulk water are goods ways to keep them well nourished. Maintaining them in very nutrient-rich shaded environments is also helpful, but then nitrates and phosphate must be kept low to prevent algae from covering their pores.

Nevertheless, questions sometimes arise as to some needing to be placed in lighted areas, and understand that because some are found in such areas in the wild. Yet not because they are photosynthetic, but because what may be living on them uses light to one degree or another and the sponge utilizes their discarded products as a nutritional source. But in the wild, in these type cases, the water quality is excellent, and water movement is just right as to benefit the species. In the aquarium, water quality is almost always less than it is in the wild, and water motion/direction is also not the same as it was in the wild where the species was originally found. Then, when placing this species in the aquarium, its poorer water quality and or water movement lends itself to unwanted algae often forming on the species, since its becoming a collection device for detritus. Soon, unwanted algae prevent the needed nutrition from getting to the sponge cells, and it then wastes away. Therefore, in most cases where sponges are involved, the shady areas in 'aquariums' probably are the safest areas, again in 'aquariums.'

Even though there appears to be three classes of Sponges, (Demospongiae; Calcarea; and Hexactinellida) only two contain anything that might even remotely interest aquarists having tropical or temperate aquaria. Furthermore, the taxonomy relating to these creatures is confusing, especially for the non-scientist, and common names may be used interchangeably for many different species making their identification even more complex.

Class Demospongiae - Most Sponges

Family Chondrillidae
Chicken Liver Sponge

This species, Chondrilla nucula, is probably one of the most talked about sponges as in is often found on live rock coming from the Indo-Pacific and Atlantic Oceans and should be removed, as it's very difficult to maintain in closed systems. In fact, it yields a strong anti-feeding chemical to withstand being fed upon by fishes. Not one of the more desirable sponges. Looks like a lump of brown chewing gum!

Family Coppatiidae
Yellow Encrusting Sponge

This is a common name used quite frequently for this type sponge, as this species Jaspis serpentina often encrusts the bottom of rocks or corals that arrive from the Tropical Western Pacific. It generally inhabits the underside of rocks on reef flats where good currents exist. Actually does fairly well in nutrient-rich aquariums or refugia designed for filtration if placed in a shaded area and where the current is quite swift (WM 2 - 3).

Family Clionidae
Red Boring Sponge

This species, Cliona delitrix, hails from the Western Atlantic: Florida, Caribbean, and the Bahamas, and inhabit reef and lagoon areas usually on or around stony coral projections. It has a temperature range of 72 to 79°F (22 – 26°C). These encrusting balloon-shaped sponges are suspension feeders and feed upon plankton and suspended detritus, and require numerous feedings per day of live and/or preserved commercial phytoplankton products or that of animal and plant powders that produce suspended products in the bulk water. Interesting and sea squirt in appearance, however if attached to stony coral it will dissolve its calcium carbonate skeleton material. Rarely seen in the trade. (WM 2 - 3)

Boring Sponge

Another in this genus, C. vastifica, hails from the Indo-Pacific and Red Sea and inhabits undersides of corals and rocks coming from these areas and has a very common name as do other similar shaped sponges. These encrusting sponges are difficult to maintain for any appreciable length of time. They, as do other sponges, feed upon plankton and suspended detritus and in aquaria require numerous feedings as mentioned for the above species. Always provide shade and an area where the current is quite swift. (WM 2 - 3)

Family Axinellidae
Yellow/Red Lattice Sponge

The species Acanthella cavernosa is one of the more popular sponges seen in the trade. It hails from the Indo-Pacific and is usually found encrusting various substrates near or in caves where water currents are fairly swift. It's a filter feeder, feeding upon plankton, bacteria and suspended detritus and depending upon where its found, varies in color and shape. (WM 2 - 3)

As with almost all sponges, it's difficult to maintain long term, therefore it should be kept in systems designed to meet its needs. Keep in mind these are not simply colorful additions to the aquarium to be placed in wide-open viewing areas, as they need careful forethought to their placement in aquaria. And if you do not have the needed environment, lets leave it in the dealers' aquarium or in the wild.

Orange Paddle/Fan/Ear Sponge

The species Stylissa flabelliformis is another popular sponge seen in the trade and it hails from the Western Pacific. Usually found with its flat side facing into the current and encrusting various rocky substrates on coastal reef shelf areas where water currents are fairly swift. It's also a filter feeder, feeding upon plankton, bacteria and suspended detritus and can attain 12 inches (30 cm) in diameter. Sometimes attains an odd growth with a second lobe overlaying the first large lobe/main growth.

Its husbandry is no different than what it is for the other sponges mentioned above. (WM 2 - 3) Even though it prefers somewhat nutrient rich surroundings, it will not tolerate any alga growth. Occasionally stirring of the substrate/sediment/sandbed will help small particulate matter (detritus) to enter the aquarium's bulk water, somewhat helping to provide some nourishment.

Family Chalinidae
Blue Sponge

If there's a sponge species that can be considered the top favorite since it's fairly easy to maintain, besides looking quite nice, it's those in the genus Haliclona. Since it would take a scientist to distinguish exact species, all seen in this genus are simply referred to in the trade with a common name, i.e., Blue Sponge. They hail from the Indian and Indo-Pacific Oceans and inhabit coral reef flats where they encrust hard substrates. It does best in a moderately 'lighted' area (PAR 100 - 200, the only one that I know of that seems to do fairly well/thrive in lighted areas), yet should have the same remaining husbandry as described above (WM 2 - 3). Unfortunately it does not ship well, but if you get a healthy piece it will usually fair quite well in reef systems.

Red Tree Sponge

Another in this genus, but better left in the wild is H. compressa, which hails from the Caribbean and is found on reef flats. It has the same general husbandry requirements as discussed above. It's often seen in the trade, but success rate with this beautiful species is quite slim. (WM 2 - 3)

Family Ircinidae
Stinker Sponge

Mentioned here simply because if this species, Ircinia felix, which hails from the Western Atlantic, is removed from the water, its smell is very bad! In fact, it serves no useful purpose in aquaria and actually yields a strong anti-feeding chemical to withstand being fed upon by fishes. Very rarely seen in the trade, but better left in the wild.

Family Agelasida
Candy Cane Sponge

This species, Agelas gracilis, is said to come from Australian waters, mainly its eastern waters including the Great Barrier Reef. It's finger like growth is encrusted with white zoanthids, possibly one of 48 known species in the genus Epizoanthus. These are non-photosynthetic/azooxanthellae filter-feeding animals and require shaded areas (PAR <100) receiving excellent water movement (WM >2). The zoanthid species, when its polyp tentacles are extended, requires at least one direct daily feeding of live and/or preserved commercial phytoplankton and/or zooplankton products, or that of enriched brine shrimp, mysis, small pieces of marine fish/shrimp flesh.

As for the sponge, and as with most sponges, it should be kept in systems somewhat normally nutrient rich or those that can be fed heavily without creating growths of unwanted algae, such as those systems designed to greatly limit phosphate and nitrate levels from heavy feedings. Difficult to maintain long term! But extremely beautiful!

Class Calcarea - Calcareous Sponges

These are sponges having skeletons composed of three or four rayed calcareous spicules, which consist of calcium carbonate in the form of calcite. Some of these sponges are yellow, while most are either a drab color or almost colorless. They are often found on the underside of rocks or in small crevices and caves. Many are encrusting while some others are cushion-shaped, sometimes with branches leading away from the main body, often forming new bodies. There are only a few are of interest to marine aquarists, and only one will be noted here. In fact, if sponges are of great interest, visit my Animal Library and open 'Sponges' in the subtopics, as it contains hundreds of species to view.

Family Clathrinidae
Yellow Calcareous Sponge

Simply a common name for this type sponge, as this species, Clathrina canariensis often encrusts the bottom of rocks that arrive from the Tropical Western Atlantic. It generally inhabits caves or is found on the underside of rocks on reef flats where good currents exist. It's generally a free-bee that comes on the bottom of live rock or coral specimens from these areas. Actually does fairly well in nutrient-rich aquariums if placed in shaded areas and where current is quite swift (WM 2 - 3).

Phylum Chordata - Tunicates

The phylum is actually divided into three subphyla, however only one is of interest to marine hobbyists and that is the subphylum 'Tunicata' which contains the tunicates and ascidians, or what is usually referred to as sea squirts. This subphylum (containing over 1500 species) is in the Class Ascidiacea, which contains two major divisions; Enterogona and Pleurogona that interest hobbyists, such as colonial and solitary 'sea squirts.'

They are mostly found on reef drop-offs and/or under overhangs, with some found at the base of corals. Occasionally they are found attached to live rock or corals entering the aquarium. Since they expel a jet of water when they contract, they have been given the name 'sea squirts.' As for the 'tunicate' label, their bodies are encased in a protective tunic, hence the name, and this supportive enclosure may be smooth or leathery and is usually attached to firm substrate.

Two openings exist in the tunic, often one larger than the other. The larger one, called the buccal siphon contains beating cilia that take in water, where it then enters a chamber called the pharyngeal basket that acts like a filter removing dissolved oxygen and various foodstuffs, where it then flows along with mucus into the oesophagus and is digested. Filtered water and resulting waste products leave through the smaller opening.

Most have male and female reproductive organs and therefore are capable of producing sperm 'and' eggs. After a free swimming or planktonic larval stage the adults live attached to a firm substance.

Unfortunately they require heavy concentrations of suspended food particles and/or bacteria laden waters. And as noted above, have a very short life span, about one year and sometimes far less. However, there are some species occasionally seen in the trade that are extremely colorful and attract hobbyists. Only those willing to provide for their demanding level of care should attempt keeping them in closed systems. Actually, 99.9% should be left in the wild.

For those that want to maintain them in aquaria, these creatures require numerous feedings per day of live and/or preserved commercial phytoplankton products or that of animal and plant powders that produce suspended products in the bulk water.

Please think twice about removing these beautiful creatures from the wild! And for more information about these pretty creatures, recommend reading "Reef Invertebrates, An Essential Guide to Selection, Care and Compatibility" by Anthony Calfo & Bob Fenner (ISBN 0-9672630-3-4).

Family Clavelinidae
Pom-Pom Tunicate

In the Division Enterogona, the species Oxycorxnia/Nephtheis fasicularis infrequently makes it into the trade. Besides the very common name mentioned above, it's also called the Blue Palm Coral, Lollipop Tunicate, or Fascicular Sea Squirt. It hails from the Tropical Western Pacific and this suspension feeder is found in protected areas receiving gentle water movement and usually inhabits areas on reef drop-offs and under overhangs.

For those that want to maintain them in aquaria, these creatures require numerous feedings per day. As described above for various sponges, phytoplankton products or that of animal and plant powders that produce suspended products in the bulk water should be used. Proper placement is also quite important, as most prefer low light/indirect light and gentle water movement. Besides being difficult to maintain, they have a very short life span, usually about one year and sometimes far less. A well-developed refugium might be a better place to maintain this species. (PAR <100) (WM 1 - 2)

Family Didemnidae

Didemnum molle hails from the Indian Ocean and Indo-West Pacific and forms colonies that are rounded or barrel-shaped (looks somewhat like a strawberry/raspberry). Body walls are embedded with calcium carbonate pigmented spicules that make them brittle and also are responsible for their color, which ranges from white to orange-brown. Its upper out siphon rim is bright green, which is caused by its zooxanthellae. Needs a well-lit environment (PAR 300) with good water flow (WM 2 - 3) and needs to be fed daily with liquid invert foods.

Family Diazonidae
Blue Sea Squirt

The species Rhopalaea crassa, which hails from the Indo-West Pacific, also shows up in the trade occasionally. It inhabits hard substrates in shallow water subject to good water movement and is a beauty, often an intense violet or blue with most specimens having a yellow edging around their inlet and outlet siphons. It's another species in this Phylum needing special attention to its feeding requirements as noted above. Probably better left in the wild as its difficult to maintain and short-lived, yet would be worth an extra effort to keep it going! (PAR <100) (WM 1 - 2)

Family Pyuridae
Golden Sea Squirt

In the Division Pleurogona, the species Polycarpa aurata is often available. It hails from the Indo-Pacific and is found on hard substrates in shallow water that are subjected to good water movement via tidal changes. It's a suspension feeder, with a large inlet siphon and smaller outlet siphon quite visible. Probably the most collected species of all sea squirts and can attain about 6 inches (15 cm) in length. The body is mostly white with some yellow around each siphon and there are also lilac colored lines and channels over much of the body. Requires the same care as described above.

Phylum Annelida - Segmented Worms

There are about 15,000 segmented members in this Phylum, with many of major interest to marine hobbyists, especially those with lots of live rock and deep sandbeds. In fact this Phylum contains very good examples of the good, bad, and ugly, with all in the Class Polychaeta which contains over 10,000 described species that are mostly marine and contains over 80 families.

Where aquarists are concerned, those of interest because of their beauty fall into the Order Sabellida, and the Families Sabellidae and Serpulidae or what is generally referred to as 'ornamental worms,' i.e., feather dusters. Many of these worms are classified according to their mode of existence, such as tubeworms or fanworms.

In fact, all Polychaetes are usually called 'bristleworms' since they have hair-like projections along their sides, even the beloved fanworms. These hairs are often used for locomotion, yet some dispense a toxin, such as the coral eating fireworms (the bad and ugly guys) in the Genera Hermodice and Eunice. Yet, even some of the bad and ugly ones have some value in healthy reef tanks, which is discussed below.

Family Sabellidae

Sabellida worms commonly called Feather Dusters construct a leathery tube, sometimes up to 12 inches (30 cm) in length, from which they extend a single crown of multicolored feather-like filaments. In the wild they are usually found buried in sand, not adhered to rocks. Their tubes are constructed of sand, detritus, mucus, and other bits of sediment. It is better to locate these worms near the bottom of the aquarium where this material is more plentiful. The fact that particulate matter is higher near the bottom of the aquarium and that they are not photosynthetic animals, are other good reasons to place them in this area.

They use their slime-coated filaments/tentacles or "feathers" as some call them, for respiration and to collect suspended particulate matter/plankton. Collected matter is then drawn towards the mouth area at the center of the tentacle ring.

Solutions containing phytoplankton and/or zooplankton (rotifers) are recommended. These feeding solutions should be applied near and under the crown of feathers so it can normally be drawn up and to the beating cilia on the feathers. It should be noted these tiny hair-like extensions generate the current that draws the food supply into the feather-like head of the animal. Dispensing the feeding solution above the animal may cause the animal to retract with most of the feeding solution going to waste.

Feather dusters may lose their crown of 'feathers' for many reasons! Among those reasons is poor water quality, being disturbed too often by tankmates, or simply the lack of sufficient foodstuffs. Even though the head of feathers is gone, the worm remaining in the tube may grow its 'feathers' back within a couple of months. However, if it returns smaller, it's an indication the food supply was inadequate and steps should be taken to increase its food supply. If this happens again, i.e., losing its feathers, the tubeworm will no doubt die. Always feel the tube for the worm body inside, and if present/some movement exists in the tube, put it back and wait for a few more weeks to see what happens.

Predators like angelfishes, triggerfishes, wrasses, most shrimp, and the arrow crab will not make suitable tankmates.

Duster Cluster

The species Bispira brunnea hails from the Tropical Western Atlantic: Caribbean, Bahamas, and Colombia and is found attached to rubble along coastal reefs. They live in a cluster of membrane-like sand and mud encrusted tubes. Individuals have single crowns, usually a light tan with white at the tips of the tentacle. Varies in size, yet crowns usually do not exceed 1 inch (2.5 cm). Generally found in the wild attached to live rock, therefore probably better if loose specimens are glued (cyanoacrylate gels) to existing rock in the aquarium, preferably at lower levels. Apply phytoplankton type foodstuffs using a turkey baster once every few days.

Feather Dusters

There are two in the genus Sabellastarte, with S. indica coming from the Indo-Pacific and Red Sea, and a similar looking species, S. magnifica, from the Tropical West Atlantic and the Caribbean. Both are found on sandy and/or rubble regions along reefs and are suspension feeders. These are the most common feather dusters sold in the trade, and proper placement is near or at the bottom of the aquarium. Solutions containing phytoplankton and/or zooplankton (rotifers) are recommended and should be applied as discussed in the family discussion above.

Family Serpulidae

Christmas Tree Worms

Unlike the Sabellida Feather Duster worms, Serpulida worms form a rigid limestone tube. The Spirobranchus giganteus species is common in the Caribbean and a subspecies is found in the Central Pacific to the Red Sea. Their radioles or 'feathers' form two spirals, each separated with a hardened operculum, a trapdoor-like device, which is nothing more than a small hinged door the same diameter of the tube and can be shut when the worm senses danger, which may simply be nothing more than a shadow passing over its structure. There are several whorls of feathers in each crown. Their tentacles radiate from a central stem area with the largest near the base of the crown, narrowing to a point at the tip. Hence the name "Christmas-Tree." These colorful, yellow, red, white, blue, purple, green, pink, and combinations of, tube worms may have a crown up to 1 inch (2.5 cm) or slightly larger.

They are found in colonies attached to live rock. Those coming from the Gulf of Mexico and the Caribbean are the largest, having radioles about 1 inch (2.5 cm) in height. They do not exist in a symbiotic relationship with other corals as do the Indo-Pacific variety (Tullock, 1997). They may be kept in lower light and water movement than the Indo-Pacific variety.

As for those coming from the Indo-Pacific area, the Christmas Tree 'worms' have a symbiotic relationship with live heads of Porites coral. It is thought the worms derive nutrition from the coral mucus (Wilkens, 1990). They require strong water movement and excellent lighting to maintain the Porites coral. Their radioles average a .5 inch (1.2 cm) in height.

To shed light on this confusing taxonomy aspect I turned to the British marine biologist and diver Vincent B. Hargreaves Ph.D. (Doctorate in Marine Biology with a double major in Ichthyology, and Marine Invertebrate Zoology) for his help to clarify the present situation.

He describes it as follows - "There are two 'groups/complex's' of Christmas Tree Worms - Spirobranchus giganteus and Spirobranchus tetraceros. In the 'giganteus complex' there are three further subgroups: S. giganteus - comprised of three species from the Caribbean and Eastern Pacific - S. incrassatus (Panama area of Central America), S. spinosus (Subtropical coastlines of southern California/Mexico), and S. giganteus from the Tropical Western Atlantic/Caribbean. In the S. corniculatus subgroup there are five species from the Indo-West Pacific and Western Indian Ocean - S. corniculatus, S. gaymardi, & S. paumotanus (found in the litoral zone, often out of the water for short periods between tides), S. nigranucha (The nearest relative to S. paumotanus, which does not have an operculum, therefore cannot trap water inside to survive low tide timeframes), and S. gardineri from the Indian Ocean, which has two or three species having a round operculum. Furthermore, those in this entire complex have their operculum between its two spirals and it has a 'double horn' on its free edge. There is also a small spike on the edge of the tube opening that fits between the double horns when the operculum is closed. Similar to a 'hasp' on a door.

As for the species in the S. tetraceros group/complex, they have distinct differences from the S. giganteus complex, as their 'trees' develop on a separate stem from the operculum, unlike those of S. giganteus. Also, they do not form a close arrangement with stony corals as they may be found on/in any type of calcium carbonate coral rubble. None of the several species in this complex have been described down to the species level as of yet, but H.A. Ten Hove, 1988, 1993, and 1994 has laid down the basics of the current understanding of the Serpulinae group."

As an added note, they reproduce sexually, as there are separate males and females. The males release sperm into the surrounding waters and if sensed by a female ready to spawn, she releases eggs. Embryos develop into a swimming larva within a few days. Ongoing culture is extremely difficult, as phytoplankton is needed for further development and I do not know of this yet occurring in captivity.

Christmas Tree rock worms coming from the Gulf of Mexico and the Caribbean have radioles about 1 inch (2.5 cm) in height. They do not exist in a symbiotic relationship with other corals as do the Indo-Pacific variety, and may be kept in lower light and water movement than the Indo-Pacific variety.

Keep in mind these worms are not photosynthetic creatures, as they are filter feeders, and their radioles/branches/pinnules collect tiny bits of detritus, bacteria, and/or plankton in the water column and send it to its mouth for sustenance. To prevent them from starving to death, they need a supply of planktonic-like foods to remain healthy and would recommend a high quality phytoplankton product be applied upstream from the species at least once a day.

Also of interest is the tropical species 'Neodexospirs sp.' and 'Vermiliopsis pygidalis,' which are the very tiny (2 mm) circular white hard-shelled feather dusters that appear in shaded areas, such as on pump bodies, live rock, and aquarium side panels. They are suspension feeders and often found in great numbers on these type surfaces.

And, last but not least, there's another very small family member, about 3 mm, and more snake-like in appearance that often shows up under live rock. They, probably a Microprotula species and these 'squiggly' shaped worms are detritus feeders.

Magnificent Tubeworm/Co-Co Worm

The species Protula magnifica, probably the largest of calcareous tubeworms, hails from Tropical Indo-West Pacific and most often inhabits dimly lit rocky regions usually on current-swept reef slopes. To hold its position in these areas, its calcareous tube is cemented to various types of firm substrates. The closed tail end of the tube is often spiraled, with its open end facing into the current, but lacks an operculum (trap door) to seal off its entrance. Its feathered head/branched tentacle crown has two spirals that collect suspended particulate organic matter and phytoplankton. Crown approaches 3 inches (7.5 cm) in diameter and its tube can be almost 1 inch (2.5 cm) in diameter and up to 10 inches (25 cm) or sometimes, much more in length. Crown colors are usually reddish orange and white.

As for placement in aquaria, a shaded area near the bottom of the aquarium where gentle to moderate currents (WM 1 - 2) may help to bring various foodstuffs is no doubt the best. Keep in mind that lower areas in the aquarium are more prone to sand disturbances that could produce current swept detritus, which is a valuable food source. In fact, give some thought to occasionally stirring of the sandbed near its location! But generally, feedings with fresh or preserved phytoplankton additives at least every other day are a 'must.'

As with the feather dusters mentioned above, these foodstuffs cannot be dispensed directly onto its gills, as the worm will quickly retreat back into its tube, and besides, it's highly sensitive to changes in light intensity and will usually quickly retreat when a shadow passes over it. Therefore, when feeding time occurs, the food additive should be slowly dispensed into the aquarium's current that impacts the worm head so as to mimic Mother Nature.

Angelfishes, butterflyfishes, pufferfishes, triggerfishes, crabs, peppermint shrimp, etc., should not be housed with this type creature as they will pick on or eat them. Actually most die within the first year of captivity due to improper/inadequate nutrition and/or poor tankmates. Furthermore, maintaining proper calcium, alkalinity and magnesium levels are extremely important with this species.

Family Amphinomidae
Bristle Worms

As for the ones that get added without our knowledge and fall into the category of 'bad guys' those in this family are commonly called bristle worms or fire worms. They generally arrive as a hitchhiker in some hole in live rock and/or in the calcareous areas of some corals. There are two mentioned here, with one being a very good scavenger of dead organic matter (Eurythoe complanata) and the other (Hermodice carunculata) a scavenger of anything it can get! Both have poisonous setae or hair-like spines along its sides, which are very brittle and can easily break off and cause a painful experience if you pick one up without gloves.

Should you ever be unfortunate enough to get stuck by these bad guys, suggest the following — dry the area by directing air from a fan or blower over the area. Do not under any circumstances wipe the area dry. Once dry, use tape such as masking, duct, or clear cellophane tape to 'blot' the area. This should allow the bristles sticking in your skin to stick to the sticky side of the tape, hopefully removing most of them. Repeat as needed. Then dab the area with rubbing alcohol or vinegar. Or try a mixture of 1 part household ammonia to 10 parts water or sprinkle a meat tenderizer on the area. This helps denature the toxin and provides a reduction in the burning sensation. When the area appears to be free of bristles and is dry, apply an over the counter antibiotic ointment. If there's lingering pain or swelling, consult a physician.

Keep in mind both of these worms can multiply quite rapidly when there is a ready supply of food. Aquarists that overfeed are inviting them to reproduce and they can do so quickly via asexual reproduction. They can also, via fragmentation, divide themselves up into new worms. Any type of food will be quickly consumed by these worms and the more food there is, the more worms. Fortunately most of those seen in aquaria are the genus Eurythoe complanata, which if small, are not a threat, as would the Hermodice carunculata species.

As for ridding the aquarium of these scavengers, suggest only removing the larger ones as they may damage or kill some corals, anemones, and clams. The smaller ones, less than 1 or 2 inches (2.5 - 5 cm) should not be a problem and may serve as a food supply for the Banded Coral Shrimp, Arrow Crab, Dottyback Pseudochromis dutoiti/fridmani, and/or the Flame Hawk. In fact, I've seen a Tubastraea polyp swallow a fire worm that crawled onto it while it was open.

If they do become large and noticeable, it may be time to bait them out. Since they are nocturnal creatures, they feed mostly at night unless real hungry! Take a whiffle ball and insert a piece of defrosted shrimp/fish flesh and wrap the ball loosely with a lot of fishing line. Use enough fishing line so the worm has some difficulty in finding its way through it to get to the bait in the center of the ball. Place the ball, weighted with a small weight, on top of a large net at the bottom of the aquarium late in the evening. Early, 'very' early next morning, the worms should be intertwined/feeding on the bait. Simply grab the handle of the net and lift the whole affair out of the aquarium.

Another fairly good method in removing these pests is using a short length, about 10 inches (25 cm), of PVC pipe. Drill some holes near each end, place a piece of defrosted shrimp flesh in the center of the pipe and fill each end of the pipe with Eheim Ehfifix media. This course plastic media makes it slightly difficult for the worm to make its way to the center bait. Once there, the worm feeds and grows fatter and will find it extremely difficult to get out if you have used the right amount of this plastic media. By lifting out the length of pipe early in the morning and pushing a rod through the pipe, any worms inside can easily be extracted. There are also small traps used for trapping fish and/or unwanted crabs, and can also be baited and used to capture these pests.

As to those real 'ugly' dudes, (come to think about it, I've never seen a good-looking worm!), a good example is in the Family Eunicida, which is the 'Telescoping Worm' Eunice torquata. It appeared in one of my aquariums and no doubt came in as a hitchhiker on some live rock from the Indo-Pacific, or possibly on a coral specimen from the Philippines.

It has an elongated cylindrical-shaped telescoping body that can reach a length of about 10 inches (25 cm) when fully grown. The prostomio (region prior to the mouth) has two eyes, various antennas (sensory appendages), and its pharynx has two jaws. Its general color is reddish brown and when first seen in my aquarium, I ran for my camera! In the wild, its usually found in shallow water under rocks. My specimen would extend itself outward in a telescoping manner in evening hours and search bottom areas for food. Ugly is probably an understatement, but found this species more interesting and the only thing I ever seen eaten alive were some baby Sexy shrimp in the aquarium, which had multiplied to great numbers. Anyway, ugly is an understatement and sort of reminded me of those aliens seen the movie 'Men in Black!' Yet never seemed to harm any corals.

Family Terebellidae
Spaghetti Worms

Most of these worms usually conceal themselves in the sand or a crevice in the rock, and live inside a chitonous tube surrounded by grains of sand. Their body remains hidden inside its tube, yet numerous thread-like filaments are fed out into the surrounding water to trap food. Very small food particles/detritus stick to the filaments where cilia on its thread-like tentacles draw particles of matter to its mouth. They, such as the species Loimia medusa, are basically harmless detritivores and interesting to watch. They are found both in the Indo-Pacific Ocean and Caribbean and are valuable additions to most sandbeds and usually arrive attached to live rock.

Family Chaetopteridae
Thread Worm

Commonly mistaken for the Spaghetti Worm, which has numerous thread-like filaments/tentacles, this creature has only two thread-like filaments/tentacles/legs, which are used to push water through a net-like structure that filters out suspended matter. These worms are generally up to 2 inches (5 cm) in length including the two tentacles (palps). They are thought to be in the Genus Phyllochaetopterus and conceal themselves in parchment-like tubes and are generally found in sand or rock crevices. Their body remains hidden inside its tube, yet these two thread-like filaments are quite visible. They are basically harmless suspension feeders and actually a valuable addition to any aquarium.

Phylum: Platyhelminthes - Flat Worms

There are three classes in this phylum having about 15,000+ species, with about 10,000 of them being considered a parasitic type creature to fish and invertebrate, such as flukes, tapeworms and the tiny flatworms that occasionally infest corals in our aquariums.

Some types/species of flat worms can easily be mistaken for nudibranchs, as their color and body shape is quite similar. However most are paper-thin oval shaped, can move quite rapidly, and do not have external gills. They 'glide' on a secreted coating of mucus and if disturbed can swim away with an undulating motion. These hermaphrodites have both male and female organs and can also regenerate from body fragments. They are carnivorous predators and generally feed upon colonial ascidians, making them almost impossible to maintain in closed systems. Occasionally they arrive on the bottom of live rock and are infrequently seen thereafter.

Of major interest to aquarists is the flat worm called 'Planaria' and actually are not among what is considered as 'parasitic' flat worms. The ones I've seen, Convolutriloba retrogemma, look like reddish-brown freckles with a forked tail and slightly rounded top. They are about the size of a freckle (.25 inch - 2 - 5 mm) and can rapidly increase in number to the point where they may cover an entire coral specimen. Mushroom and leather corals seem to be a favorite gathering place. They are thought to be harmless (Sprung, 2000) yet unsightly, however they will suck out body fluids containing zooxanthellae. When in great numbers they can also block light from reaching photosynthetic animals.

When there is an abundance of them and if possible, remove the infected specimen and give it a 5 to 10 second freshwater dip. Almost all the flatworms will drop off and any remaining can be gently brushed off. Caution, not all corals can withstand a freshwater dip.

Since these worms are photosynthetic, they are attracted to light. Placing a lamp near the aquarium side panel at night will attract them in huge numbers making it easy to siphon out the majority of them 'very' (before sunrise) early the next morning. The reduced number may give other biological control methods a better chance at bringing their numbers under control.

As for biological controls, the Banded Goby, Amblygobius phalaena, is said to eat this flatworm. Also, wrasses, e.g., the Sixline Wrasse Pseudocheilinus hexataenia, Leopard Wrasse Macropharyngodon meleagris, and Yellow Wrasse Halichoeres chrysus. Also some anthias are thought to be an efficient consumer of this pest, as are Peppermint Shrimp and also those in the Lysmata genus. In fact, the Mandarin fish Synchiropus splendidus has cleared up the problem in some of my past reef systems. Also, the Sea Slug/Nudibranchs in the genus 'Chelidonura' are believed to be a very good consumer, although very short-lived slugs. Also, scooter blennies and hawkfishes may also consume them.

There is also some thought these flat worms can rapidly go away due to some biological clock, lack of foodstuffs or a biological competitor. Also, there's some thought the over use of iodine supplements, which flat worms may concentrate in their internal fluids, may lend itself to promoting their proliferation. Therefore, there's some thought that killing these flat worms, such as Convolutriloba retrogemma in large numbers could present a toxic condition in the closed system by stripping its oxygen in the degradation of large numbers of these pest flat worms and in the release of iodine in some format, as they harbor it in their tissues. Increased water flow and improved protein skimming would then be very helpful. Highly recommend caution with any products said to rid these pests, as what is killed and remains visible should be siphoned out quickly to prevent water quality from degrading!

And now, move on to Section Six, where you'll find my final words in this vast work, along with a possible chart of interest, a list of books to read or reference and a Glossary that might be helpful.