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By Bob Goemans
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Surgeons in My Aquariums

Authored by: Bob Goemans

First printed in TFH, December 2006

These fish belong in the “Order Perciformes” and “Suborder Acanthuroidei” as members of the “Family Acanthuridae” (Surgeonfishes), which includes 2 Subfamilies, and 6 genera containing approximately 72 described species. They are a large circumtropical family consisting of fishes with disc-shaped, laterally compressed bodies, such as Angelfish and Butterflyfish. Mostly algae grazers, they are generally found in shallow reef areas and lagoons.

The Subfamily Acanthurinae contains the majority of the species, and have three anal spines, with the caudal peduncle armed with one or more spines. In the Acanthurus and Ctenochaetus genera, which are in the Acanthurini Tribe, their spines are set in a deep groove in the caudal peduncle and only sideways tail movement against the opposite spine can erect it. And since these spines are extremely sharp, handling these fish can be quite dangerous. However, there is an exception in this Subfamily, and that is the genus Prionurus. It has 7 describe species, and all lack retractable spines and instead have three to ten bony plates on the caudal peduncle. They are rarely seen in the trade, probably because they live in more temperate waters.

The Subfamily Nasinae has only one genus, with about 17 described species. Even though most are too large for the average size hobbyist aquarium, about 75 gallons, some have special interest because they have a forward pointing projection or outcropping below the eyes that increases in length with age. Because of this they are often called ‘Unicornfishes.’ They also have two anal spines and the caudal peduncle is armed with one or two bony plate-like spines that are sharp and used for self-defense.

These fish are generally called Surgeonfish or Doctorfishes because of the scalpel-like spines at the base of the tail, or Tangs because of the German word Seetang (seaweed), which relates to their eating habits. In fact, the Greek word "acanthus" also relates to a scalpel-like spine just before the tail, hence their scientific name.

These are predominantly herbivorous fishes, although some also eat zooplankton and detritus and have grown in popularity with many reef keepers as some play an important roll in controlling unwanted algae growths in many aquariums, although, some do have specific preferences. Even though mostly considered herbivorous fish, in the aquarium they should be considered omnivorous fishes, as they also consume meaty type foods.

Some of these species grow quite large, with some attaining 24 inches (60 cm) in length, yet those aquarists generally prefer are in the 7 – 12 inch (17.5 – 30 cm) range. In fact, a 75-gallon aquarium ought to be considered the minimum size for many of these fish as they are active swimmers and require plenty of open space, strong water currents, and some areas to take shelter. And it’s also important to remember they are mostly constant browsers and even though they have small mouths, they have large appetites. They do not fare well on once-a-day-feedings!

Furthermore, I’ve found when different Tang species of the same size and general color were mixed in the same aquarium, it often created stress problems, and in some cases, that’s putting it mildly! And because they have little body mucus, stress can cause an outbreak of Marine Ich. Therefore, ‘Tang’ tankmates should be dissimilar in size, color, and shape. Once a pecking order is established, peace usually returns. Some species, e.g., the Yellow Tang and the Regal/Blue Tang, always seem to tolerate each other. In fact, those in the genus Ctenochaetus were also were very tolerant of other Tang species.

Over the last twenty plus years I’ve had one or more Yellow Tangs (Zebrasoma flavescens) in systems from 75 gallons to 320 gallons. They hail from the Northern Indo-West Pacific to Hawaii and generally inhabit outer reefs and shallow lagoons. And I’ve always tried to be sure those purchased came from Hawaii, as then I could be sure they were not captured with cyanide. Additionally, I’ve always purchased them as small as possible, usually about 3 inches (7 cm), which is about half their full length in the wild. In my smaller tanks, one would be the limit, yet I’ve kept three in the 320, however, made sure each was different in length so a peaceful pecking order could be established, thereby preventing any undue stress from those of equal size fighting over who would be top dog (fish) in the aquarium. And when other genera tangs were added; only if there were sufficient swimming space, I added only those quite different in coloration or shape such as the Blue/Regal Tangs (Paracanthus hepatus), which is more a zooplankton feeder, than an algae consumer.

As for feeding my Yellow Tangs, in fact most of my different species Tangs, a variety of different algae was/is fed, and I’ve gone as far as separately raising tasty macroalgae such as Caulerpa mexicana and C. prolifera. I should also note that ‘many’ years ago I thought Iceberg Lettuce was a suitable foodstuff, but over the past decade came to realize that this was an incorrect assumption, as its very high in cellulose, which may clog their digestive tract if fed too often. In fact, when the above mentioned macroalgae was not available, I feed various amounts of Romaine lettuce (Romaine lettuce provides a source of ALA, one of the three important Omega-3 fatty acids, and if anything, is a much better choice than Iceberg lettuce), broccoli, green peas, and various seaweed (Nori), e,g., Palmaria palmata, Porphyra yezoensis, and Porphyra umbilicalis (an excellent source of protein, along with various vitamins, minerals, and lipids, and which is found in commercial over the counter brand name products.) and of course Spirulina, which is one of the best all around green foods. Furthermore, I recommend ‘not’ feeding Spinach too often as it contains oxalic acid, which can cause crystals to form in the kidneys (G. Blasiola, pers. com.). In fact, most of these people green foods are high in nitrate, which may sooner or later result in higher levels of nitrate in the aquarium bulk water. Yet, occasional feeding of these greens can add fiber and help keep fish digestive tracts clear, with the word ‘occasional’ being the key word. And since many of these fish are grazers, much like the cows in the meadow, they like to feed all day, and in aquaria need either frequent feedings or supplies of food such as the dried kelp/Nori made available for browsing on for most of the day.

The Sailfin Tang, or sometimes called the Red Sea Tang, Zebrasoma desjardinii, was another favorite. But because of its larger size, about 16 inches (40 cm) in the wild, it was only kept in my larger aquariums, i.e., 125 gallons and larger. It hails from the Indian Ocean and the Red Sea, and is another herbivore that prefers a wide variety of green foods, as mentioned above for the Yellow Tang. Because of its size, it was usually one of the largest fish in my aquariums and it became somewhat aggressive towards smaller family members and even other smaller fish. Nevertheless, if the aquarium was not overcrowded, it was mostly peaceful, and a good consumer of filamentous algae and even some bubble algae.

Another smaller Zebrasoma species kept was the Brown Tang Z. scopes. It hails from the Tropical Indo-Pacific and Red Sea and is another herbivore requiring an assortment of green foods as mentioned in the Yellow Tang discussion above. However, I found it to be quite territorial and seemed to prefer areas in the aquarium where there were no tankmates and/or competition for foodstuffs. In fact, was not satisfied with its demeanor and traded it back to the store where it was purchased for credit toward a future purchase.

I also tried the Black Tang Z. rostratum, which was an expensive acquisition, as it cost well over 200 dollars about five year ago! It hails from the Eastern Central Pacific such as the Line, Marquesan, Society, and Tuamoto Islands to the Pitcairn Group and gets about 8 inches (20 cm) in length. Its requirements were not any different than those for the Yellow Tang; however, this one expensive specimen was kept without other family members in a 180-gallon reef system. It did well in the system for three years, and finally was made an offer I couldn’t pass up from a local client, who just had to have it!

Several different specimens of the Sailfin Tang, Z. veliferum were kept in various large aquariums over a span of about ten years. Probably one of the largest tangs, as it gets to about 16 inches (40 cm) in the wild, and its needs were no different than others in this genus. It did like browsing on filamentous algae, which made it and its peaceful disposition a valuable plus in some of those aquariums. I should mention it looks much like Z. jardinii, (which I’ve also had on several occasions) with the only difference being the small circular spots on the snout area of Z. jardinii. And I should also mention that I recommend purchasing Z. jardinii, rather than this species, as it’s a Red Sea fish that just about guarantees its not captured with cyanide.

One of the more popular and beautiful Zebrasoma species is the Purple Tang, Z. xanthurum, which hails from the Red Sea. I’ve had this somewhat smaller species, about 10 inches (25 cm) in the wild, in several aquariums. It basically required the same care as Yellow Tangs, however, does not get along well with members of its own family. Yet, I did keep one with a Yellow Tang in a 220-gallon reef system, and even though there were a few minor entanglements, there was no damage to either fish.

Another favorite has been the Blue/Regal Tang Paracanthus hepatus, which if possible, I kept in small groups. Again, I would purposely purchase different size specimens so as to keep a peaceful pecking order. These hail from the Tropical Indo-Pacific, and inhabit areas heavy in algae growth, however, are more a meat eater in aquaria. And, because of that, fed them meaty foods such as fortified brine shrimp, both live and frozen, finely chopped fish and crustacean flesh, and mysis shrimp. And over the years found them always to be first in the aquarium to show signs of Marine Ich, therefore began keeping the cleaner shrimp Lysmata amboinensis in their aquariums, as the shrimp would prevent this malady from gaining a foothold. And I often kept up to six of these shrimp, depending upon the size of the aquarium and its other inhabitants, so there were always cleaning stations open to service them. This ‘always’ was quite successful in keeping them healthy!

As for the genus Ctenochaetus I often kept the Koli Tang Ctenochaetus strigosus, sometimes called the Yellow-eye Tang or Bristletooth Tang. It hails from Indo-Pacific, and is usually the most inexpensive in the family because of its dull brown color. But its desire to constantly browse on microalgae/microcrustaceans and its peaceful nature, besides its fairly small size, about 7 inches (17 cm) fully grown, made it a good choice in many of my aquariums. And note, only keep one per tank, as they will do battle with members of their own species.

My favorite in this genus was C. hawaiiensis, the Chevron Tang, another quite expensive selection. It hails from the Central Pacific and as a juvenile, it’s extremely pretty, with a blue herringbone pattern over an orange colored body with blue on its fins. Unfortunately, as it grows to maturity, it turns an olive-brown. It’s a constant browser, feeding on microalgae, detritus, and microcrustaceans, and I should note, found it to need a more varied diet, as do the species mentioned above.

I’ve also maintained many different species in the Acanthurus genus. The Achilles Surgeonfish A. Achilles; the Power Brown Surgeonfish A. japonicus; the Powder Blue Surgeonfish A. leucosternon; the Lined or Clown Surgeonfish A. lineatus; the Orange-shoulder Surgeonfish A. olivaceus, to name some of them. The Achilles Surgeonfish was a gift from a local client that had bought it, and then decided his tank was too small for it. It went into a 180-gallon system, where it browsed on different algae, but never became a good tankmate, as it did more swimming than eating. I finally gave it to a local shop. As for the Powder Brown and Powder Blue, I found them very nervous fish, constantly on the go and finicky eaters, and also ‘very’ susceptible to Marine Ich. The Orange-shoulder Surgeonfish was purchased to try and control a bubble algae outbreak, and even though it faired quite well, did little to decimate the unwanted algae. I found the Lined or Clown Surgeonfish somewhat difficult to feed, as it was somewhat underfed when I purchased it and/or was already too mature and accustomed to the foodstuffs in the wild to be enticed to feed on available aquarium foods. It was another Tang that was eventually returned to the shop where it was purchased and was granted credit towards a future purchase.

And then there was ‘Harry,’ a Naso Unicornfish that I kept about twenty years ago in a 320 gallon system. In fact, at this stage in my life I’m not quite sure exactly what species that was! But if any of those that are reading this have ever kept a pufferfish, such as the dogface puffer, you’ll know that certain fish can become ‘child-like’ and follow its keeper when he or she enters the room. Well, Harry got like that after I had it for about six months. If I sat on one end of the couch in front of the aquarium, Harry would come over to the end of the aquarium facing me and just hang there looking in my direction. If I moved to the opposite end of the couch, Harry would then swim to that end of the aquarium and hang there until fed various different meaty foods. Even when fed, Harry would mainly stay in the end of the aquarium across from where I was sitting. Okay, I know your thinking ‘why did he name it Harry?’ Well, we had a relative named Harry that was always looking for a handout. And my wife thought that would be fitting! Actually, Harry the fish was like a member of the family, just like a cat or dog may be in your household!

I hope you enjoyed reading this ‘look-back’ on my keeping of various surgeonfish.

Kingdom: Animalia

Phylum: Chordata

Class: Actinopterygii

Order: Perciformes

Suborder: Acanthuroidei

Subfamily: Nasinae

Genus Naso

Subfamily: Acanthurinae

Tribe: Prionyrini

Genus Prionurus

Tribe: Zebrasomini

Genus Paracanthurus

Genus Zebrasoma

Tribe: Acanthurini

Genus Acanthurus

Genus Ctenochaetus

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