Saltcorner
By Bob Goemans
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Aquarium Systems (Instant Ocean) 

The captive breeding of tropical reef species for the aquarium trade, with specific attention to long-term planktotrophic larvae

Authored by: Rob Toonen

Although breeding aquarium animals is a natural goal for most aquarium hobbyists, saltwater enthusiasts have a much more difficult task before them than do freshwater aquarists. Here I present the basic modes of reproduction among marine animals, and discuss the particular challenges that face an aquarist in their attempts to breed marine organisms at home. Probably the largest hurdle for any marine aquarist attempting to breed reef animals at home is providing sufficient and adequate food for the tiny free-swimming babies (larvae) that the vast majority of marine organisms produce. Culturing the marine phytoplankton and microscopic zooplankton necessary to feed larval reef animals often turns out to be considerably more complicated than actually raising the juvenile fish or invertebrates themselves. Securing a reliable food source of the appropriate nutritional value and particle size to feed the larvae is often the most critical step in being successful at rearing any species at home. Provided that a suitable food source is secured, there are some simple larval culture techniques that are easily adapted from the laboratory to the home for raising the larvae. However, the process is often long and complicated. Therefore, successfully raising any species of marine organisms at home remains a challenge that relatively few aquarists can claim to have conquered. Hopefully this brief introduction will wet the appetite of some potential breeders out there and encourage more people to give it a try…

As marine aquarists become ever more aware of the environmental and conservation aspects of our hobby, captive-raised animals are becoming more common and more desirable to the average consumer. Many people believe that legislation is likely to force the hobby to make a much more significant effort to develop captive breeding programs to meet the hobby demand, and that sooner or later some substantial proportion of the organisms traded will be farmed rather than wild-caught. There are certainly a number of captive breeding facilities out there, and some are producing a variety of fishes (such as clowns, sea horses and dottybacks) corals, clams and other invertebrates, and even “live” rock and sand. Others are currently farming live foods, such as phytoplankton and zooplankton to provide a more nutritious and natural diet to many of our precious aquarium inhabitants. However, despite the fact that these animals and products are becoming more widely available through local petshops, consumer support for these facilities has been far from overwhelming. Despite the best intentions and voiced support of many hobbyists who want to do the right thing, consumer knowledge of, and demand for captive-raised animals remains relatively low. The bottom line seems to be that wild-caught animals are cheaper, and whether it is because they simply don’t know better, or don’t care, people continue to search out the lowest price for their animals regardless of the source.

While it is natural for people to want the most reasonable price on whatever they choose to buy, I hope to convince you that there is more at stake than simply the price of the animals to consider when you are making a purchase for your aquarium. For example, the Philippines and Indonesia are among the world's largest exporters of ornamental marine fish for the aquarium hobby trade. Numerous sources have reported that many of the fish collectors in these countries use cyanide solutions to stun tropical fish, and make them easier to capture. The widespread and repeated application of cyanide solutions not only results in permanent damage to the coral reefs on which fish are collected, but are also typically results in damage to the aquarium fish that are collected in this way (and sometimes the collectors as well!). A number of sources have reported that damage to the internal organs of fish collected after being stunned with cyanide results in complications that almost always result in death within a year of the time from capture. This proves to be a problem only to consumers who purchase these fish for display aquaria, because they show no obvious external signs of cyanide poisoning (indeed our inability to detect which fish may have been cyanide-caught remains the major hurdle in preventing this destructive practice), and the several months that it takes for the fish to eventually die is plenty of time for them to be shipped and sold before the fish suddenly dies for no apparent reason in your aquarium at home.

Most experts agree that the majority of deaths among marine ornamental fishes are a result of the stress related to capture, shipping and display of these animals in the most cost-effective manner rather than the manner that provides for the best chance of success with the animals. Some of these stress symptoms can be quite obvious (such as disease, external damage or the like), but many appear to be much more subtle, and we are only now beginning to understand that fish deaths even months after they have settled into their new home may be related to the stress they experienced during their capture and transport. Morgan Lidster reported at the Western Marine Conference last year that in some species more than 90% of the fish that appear to have shipped well, been eating and (by all outward appearances, at least) healthy died with a few months in a well-maintained aquarium (such as the Flame Angel, Centropyge loriculus).

These types of issues led to the formation of a company that was devoted to the sale of only certified net-caught fish that were harvested in a sustainable manner from natural reefs. They felt that “many purchasers, both retail stores and individual buyers, would be willing to pay a little more in return for our focus on avoiding cyanide contamination. And we also believe many aquarium keepers may choose to contribute to a realistic plan that will substantially reduce cyanide use if we are able to implement our program effectively. Thus, we expect our marketing of cyanide-free fish will set an industry standard that many buyers will insist other operations must meet as well.” Sadly, they were recently proven wrong: the cost of cyanide-free fish from reliable sources is consistently higher than the cost of wild-caught fish sold without concern for the method by which they are collected, and in the end, there simply were not enough retails who were willing to pay higher prices for healthier fish that were harvested in an ecologically preferable manner. As I said above, the bottom line is that the aquarium industry is extremely price-sensitive, and regardless of the amount of talk about being more environmentally-friendly, there appears to be little concern for such issues when it comes to how much you and I are willing to spend when we’re standing in line at the local fish shop...

I would be willing to bet that most people who are serious about their aquarium enjoy the hobby because they love the animals and appreciate their natural beauty. I doubt that many people would want to maintain a reef tank if it meant that they were destroying the natural reefs, and would never be able to see the splendor of a natural reef in the wild. Well, folks, talk is cheap, so put your money where your heart is, and start to ask your local retailers where the fish you want to buy are coming from. If you are lucky enough to have a supplier who stocks captive-bred animals, or can get them for you, I encourage you to support those dealers and make sure that you, at least, are not part of the problem.

Another way that many reef aquarists are helping with the effort to minimize the demand for wild-caught animals is by starting to rear many of the more popular animals at home (particularly corals and clownfishes), and trade or sell them locally. My purpose in writing this article is twofold: first, I hope that the little soap-box sermon above has increased your awareness of the fact that there are captive-raised animals available from a variety of suppliers (you need only do a little searching on the web, or ask your local retailer); second, I want to very briefly explain the basics of what is involved in captive breeding for marine animals in the hopes that more people will try at home. Many people who keep saltwater aquaria have had at least some experience with breeding freshwater fishes, but some things are very different when it comes to marine animals, and I want to provide a brief overview of what it takes to actually start breeding some of your favorite reef critters at home.

Now having said that, I really have to point out that it is impossible to cover the detailed techniques of breeding any organisms in such a short article, and instead I will refer readers to the work of authors such as Moe, Wilkerson and Hoff, or even the vast literature of the commercial aquaculture industry for more detailed descriptions of the methods of marine animal culture (there are a number of good resources on the Web). I also encourage interested readers to contact the Breeder’s Registry, a nonprofit organization founded by Stan Brown, which facilitates the exchange of information among people ranging from the average hobbyist to professional aquarists, who are interested in the captive breeding of marine animals. The Breeder’s Registry has a searchable database of reports outlining the aquarium conditions, spawning and rearing requirements of literally hundreds of marine species compiled by its members available online, and I strongly encourage anyone seriously interested in the captive culture of marine animals at home to first check the information available on their web site ().

Background:

Before describing the techniques involved in captive culture, I’ll try to give some background information about reproduction of marine animals in general. There are two ways in which animals can reproduce: sexually and asexually. If the animals are asexual, then a single individual can split itself into multiple copies and develop into a genetically identical group or colony. An example of this would be the growth and propagation of a coral – each polyp is capable of splitting and giving rise to another identical copy of itself. In this case, there is obviously little special care required for propagating such animals at home - there are plenty of articles and web pages dedicated to the captive proliferation (a.k.a. “cutting” or “fragging”) of corals, so I will not discuss this subject further here. For sexual reproduction, at least two individuals (a male and female) are usually required. I say usually, because the sexes are not always separate in marine animals, and if a single animal possesses both male and female reproductive organs at any point in its life, the species is said to be hermaphroditic. Simultaneous hermaphrodites are those that possess functional male and female gonads during the same reproductive season (and are often capable of reciprocal fertilization in which both animals go away pregnant from a single mating). In general simultaneous hermaphrodites do not tend to fertilize themselves, and so frequently (but not always), two individuals are still required for successful mating. Sequential hermaphrodites, on the other hand, are those that never possess functional gonads of both sexes at the same time, but rather "change sex" at some point in their life (sometimes repeatedly). The "typical" pattern of protandrous hermaphroditism is that younger/smaller individuals will be the male, while older/larger individuals will be the female (this is the case with many fishes, for example, Amphiprion ocellaris- the Common or False Percula Clown). An example of a sequential hermaphrodite would be Stenopus hispidus (the Coral Banded Shrimp), while the popular Lysmata amboinensis (the Scarlet or Skunk Cleaner Shrimp) is an example of a simultaneous hermaphrodite.

Within the broad category of sexual reproduction there are three primary developmental modes common among marine invertebrates, some of which are much easier to raise than others. Although this is a gross oversimplification (see for a more detailed account), the three primary modes of sexual developmental common among marine organisms are:

1) DIRECT DEVELOPMENT, in which larvae are either held by the parent or within an egg case, or the larval stage is bypassed entirely;

2) LECITHOTROPHY, or non-feeding development, in which free-swimming larvae are released fully provisioned with yolk and do not feed in the water column prior to settlement and metamorphosis into the adult body form;

3) PLANKTOTROPHY, or feeding development in which larvae must feed in the water column before becoming competent to settle and metamorphose.

These larval types can vary dramatically in the length of the developmental period necessary for the animals to mature before they are capable of settling and metamorphosing into the adult body form. A very rough guideline is that planktotrophic larvae typically spend weeks to months swimming about before being competent to settle; lecithotrophic larvae usually require hours to weeks before settling; and direct developers typically spend no time in the water column, although there are plenty of exceptions to these time lines. For example, the sea star Mediaster produces non-feeding lecithotrophic larvae that can remain in the water column for a year or more before settling and metamorphosing into the adult body form!

Obviously the chances of success with breeding an animal at home will depend largely on their larval duration and needs. In the home aquarium, those species with nonfeeding larvae that spend little or no time swimming around (i.e., direct developers and even some lecithotrophic larvae) have the best chance of reproducing without any special care or attention of the aquarist. On the other hand, species with larvae that require feeding, or even nonfeeding species that swim for weeks or months while developing, will almost always require special care to be raised successfully at home. Unfortunately for us as hopeful breeders, it is this last group (species with larvae that require special care) that is found in roughly 80% of coral reef animals, and these are the most difficult to rear successfully. Therefore, I will focus primarily on an overview of the requirements of these larvae and what to expect when trying to raise any species with such larvae at home.

Modes of larval development:

It is virtually impossible to generalize about the developmental modes of most groups of invertebrates because there is such a diversity of both species and developmental modes within each group, but there are a number of generalizations at various taxonomic levels that can be made (see Table 1). This is of course, a thumbnail sketch of marine invertebrate taxa and their developmental modes, but it should at least give you a rough idea of what you may be getting into if you really want to breed a specific organism in your tank. If you can get a specific ID of your animal, you can use the library of a local University or the Web to search for specific information on the developmental mode and larval planktonic lifespan of that species. Sometimes, if you’re lucky, there will be a breeders report filed for the species you hope to raise on the Breeder’s Registry website, and that will provide you with a wealth of information about how someone else raised that animal. Don't be too disappointed if you can't find any information on your favorite animal, however! Even with species that are both common and well known, the developmental modes, durations and especially settlement inducers of many marine invertebrates frequently remain a complete mystery to science. It is important information, however, and knowing the larval developmental details of coral reef species is of general interest to both hobbyists and scientists. So, if you manage to breed some reef animal at home and can document the developmental pattern/time scale and larval planktonic life span, you should be able to publish that information in one of the hobby magazines or in some cases even in certain scientific journals. If you are a serious home breeder, and want more information about or help with publishing your findings, please contact me.

Trial and error are one way to determine the developmental mode of whatever larvae you are trying to raise, but the surest way to deal with any species for which the developmental mode is not known is simply to treat them as long-term feeding larvae, and just see what happens. That may not seem very satisfying, but I’m afraid that it is often the best that you can do if you know nothing about what the animals need during larval development. In fact, it is essentially what research scientists do when approaching culture attempts with a new species about which nothing is known.

Culturing food for larvae:

The very first step, if you hope to raise any species which has feeding larvae, is to establish a reliable culture of food for the larvae. The majority of questions that I receive about larval culture start with something to the effect of: I have an animal that has just spawned in my aquarium, but I have no idea how to raise the larvae, what do I do now? Although it may sound callous, the honest answer is to write them off and start preparing for the next batch of young. If the babies have already arrived, there is little chance that you’ll be able to gather everything you need to raise them before they die, although there are now a number of online vendors who sell live phytoplankton and zooplankton cultures that can be shipped overnight to get you through the crisis. In general, however, the best approach is to establish feeding cultures and gather all the equipment you’ll need so that you’ll be prepared in advance for a spawning event. I emphasize this because almost invariably, when people try to culture an unexpected arrival, they will not only fail and lose the batch of larvae (regardless of the effort invested), they will also usually become discouraged – after all, if you tried that hard and failed to raise any larvae, why bother in the future? It doesn’t matter who you are, or how much experience you have with larval culture, if you are not set up with the equipment and supplies to care for the larvae in advance of the actual arrival, there is almost no chance that you’ll be successful in actually raising any of them. Don’t get discouraged by that fact, and instead prepare for success and be ready the next time around!

Believe it or not, the hardest part about raising any larvae that requires feeding is not the actual care and culture of the larvae, but of the microscopic food to feed those larvae. In the vast majority of cases, you'll need to grow or buy algal (phytoplankton) cultures to feed those larvae. Culturing greenwater always sounds very easy, and in fact it is not difficult (I have written articles about this in the past, and won’t go into detail about it here), but in reality, there is much more to providing a nutritional food that will support the growth and development of larvae than simply dumping green water into your feeding cultures. A number of studies have shown that larval growth and survival depend more on the nutritional value of the food than the actual type of food provided. What that means is that the same species of phytoplankton can range from highly nutritious to downright toxic depending on the conditions under which is was cultured, and although it is easy to grow greenwater at home, the nutritional value of that culture can be highly variable depending on whether or not you know what you are doing. Despite the fact that culturing your own phytoplankton is not very difficult, it is certainly not fun, and most people actually have more trouble getting the algal cultures running well enough to start raising larvae than they do raising the larvae themselves! Fortunately, there are now a variety of sources for obtaining ready-to-feed phytoplankton cultures from a wide range of suppliers, and even zooplankton such as rotifers, copepods and mysid shrimps are now becoming available through commercial vendors as well. Although dead foods are always cheaper than live, it is usually much more successful to spend the extra money and get live food when attempting to breed your animals. Frozen or preserved plankton foods function exactly as flake food: when uneaten food remains in the tank, it quickly degrades water quality. With live phytoplankton, the uneaten food not only remains in the tank, but if provided with the correct conditions, can actually aid water quality by taking up some nitrogenous wastes from the larvae as it grows and reproduces in the culture aquarium! I have discussed the relative benefits of various plankton foods in great detail in my June 2001 Invert Insights column, if you’re looking for more detail on this subject.

The standard feeding concentration for larval cultures is something on the order of 50,000 phytoplankton cells per ml of culture and that should be provided either day, or 100,000 cells every other day when the cultures are cleaned. Whether you can get away with cleaning and feeding every second day will really depend on the sensitivity of the larvae and the cleanliness and care you use in your culture techniques. Well, that’s all well and good, but exactly what does 50,000 cells per ml of culture mean in plain English? Many of the vendors who ship phytoplankton products will provide an approximate cell count for their products, and you can use that to calculate the amount that you will need to feed to your cultures (50,000 cells per ml times 1000X the volume of your culture aquarium in liters divided by the number of cells per ml in the product will give you the feeding volume you need to add). Or, you can use the “eyeballing it” method: at 50-100,000 cells per ml, the culture water should be just slightly clouded green with phytoplankton after feeding. I mean it when I say slightly cloudy – it is important to realize that if you overfeed, it will lead to more bacteria and debris in your cultures, your larvae will actually grow more slowly and you will certainly lose more (perhaps all of them); it is actually better to underfeed your cultures than to overfeed them. I have done experiments in which I fed larvae on 1/10th rations and showed that although the larvae grew much more slowly, the same proportion of them eventually survived and grew into healthy little adults (within reason of course, if you completely starve your cultures, the larvae won’t develop at all).

One of the most important things to keep in mind when trying to culture larvae is that, even more so than the adults, larvae are very VERY sensitive creatures. You must never wash the culture containers with any detergent - use hot water and lots of elbow grease to keep your culture tanks clean. If you’re worried about the cleanliness of your containers, an acid bath (swimming pool ‘pH down’ is typically sodium bisulfate, which works well for a cheap acid bath) is the best way to give them a very thorough cleaning (this typically works better than bleach which is difficult to rinse completely) once a week or so. Whether cleaning with hot water or acid, always rinse your culture flasks several times with fresh water before standing them upside down and allowing them to air dry (and if you have access to DI/RO water, it is best to rinse a final time with that). I like to use 2 culture jars for each culture I maintain so that I can alternate them and give the used one a really good cleaning while the larvae are moved immediately into the dried jar from the last cleaning. You must also avoid using any hand cream or any other lotions on your hands, and should not use soap to wash any of your culture equipment, and make sure you rinse your hands very well with lots of warm water every time you plan to work with your cultures. You will also want to avoid using paper towels for drying anything in your culture equipment - we have found that some brands contain enough chemicals to alter or even stop the development of larvae. Avoid the use of any sprays (like disinfectant, deodorant or especially pest aerosols) in the room where your larvae are to be kept. You must prevent any contaminants (like heavy metals, fixatives, detergents, solvents, nicotine, etc.) coming into contact with the dishes to be used for culture, and they should be of an inert substance, like glass, polypropylene or acrylic, that are resistant to corrosion by seawater. Larval development is a very touchy process, and after spending all the time and money/energy to set up for home breeding, you don’t want to overlook anything that interferes with the developmental process and prevent you from raising larvae!

Larval culture techniques:

There are nearly as many different techniques for raising larvae as there are people who have successfully done it. Of course, everyone will explain their personal method is the best (after all it is the one that they have chosen because it works better than any other), but the bottom line is that the best method is quite simply the one that gives you the best results, and that will vary from person to person. In the interest of space, and in keeping with the tradition that “my method is best, just ask me,” I am only going to describe one method for larval culture in this article. I think that this is an effective method of raising larvae that requires the least amount of work and special equipment of the variety of options. If you’re serious about trying to raise animals at home, I’d encourage you to take every piece of information available to you and distill the various methods and tips down to some hybrid technique that will work best for your specific application. Again, I think that the Breeder’s Registry is an excellent resource for this type of information.

Perhaps the simplest method of raising larvae is in small-scale cultures kept in a series of deep glass bowls (like custard bowls or wide-mouth highball glasses, etc.). These should be fairly large if you want to culture a reasonable number of larvae, because you should ideally limit your culture density to a maximum of 1 larva per ml of water in the container (and ideally 1 larvae to each 2-4 ml). You’ll also need something (such as plastic wrap) to loosely cover the bowls (primarily to decrease evaporation and prevent anything from falling into the cultures), and a good quality pipette (= fancy eye dropper, the reason you want a good one is so that you can reasonably remove larvae from the culture without having to suck them up one at a time - if you haven’t ever seen a typical research pipette, the glass part is finer and more tapered than your average eye dropper, and the rubber bulb is about 3-4 times the size of an average eye dropper). That is really the only equipment you’ll need to culture larvae on a small scale (hundreds to thousands of larvae) at home, although depending on your climate, you may also need to have a water bath in which to stand these culture jars to ensure proper temperature regulation. It would also be nice (but certainly not necessary) to have a stereo dissecting microscope to examine the larvae from time to time as they grow, both for sake of curiosity, but also to watch for clumping (caused by high bacterial growth) and deformities or illness. Depending on the species you are culturing, you might also like to have some cetyl alcohol (1-hexadecanol – C16H34O – looks and feels like soap flakes) around to sprinkle a few flakes on the surface of the culture water. Many species have larvae notorious for getting stuck in the surface tension of the culture vessel (especially delicate species such as nudibranchs). Cetyl alcohol is an evaporation retardant that acts to decrease the surface tension and reduces the likelihood of trapping larvae in the air-water interface. There are other ways to accomplish this feat (such as “bombing” the larvae back into the water by dripping water on them individually twice each day), but adding a few cetyl alcohol flakes to the surface of the culture is probably the simplest method if you can find it.

The party line among most larval biologists is that artificial seawater is inadequate to raise most species of marine invertebrates, but my experience is that reef tank water sometimes works just fine. Newly-mixed seawater (I have tried a wide variety of brands) does not turn out to be nearly as successful as aged tank water (or better yet, filtered natural seawater) for raising larvae, in my experience, however. My guess for the reasons behind this (and I freely admit it is just that - a wild guess) is that there is a lot of dissolved organic matter (DOM) in our reef tank water that is lacking in freshly-made artificial seawater but appear to be important to a wide variety of marine larvae, even some of those that do not appear to feed. Also, some of the buffers and stabilizers commonly added to rapidly-dissolving artificial seawater mixes (e.g., Tris-EDTA) are considered toxic to most larvae, regardless of adult tolerance to the chemical, and may prevent successful culture with freshly mixed artificial seawater. Together, these concerns suggest that aged tank water from a reef aquarium with excellent water parameters, or filtered natural seawater will be your best bet for the culture of most larval species rather than freshly mixed artificial seawater. If you only have access to artificial seawater, I suggest that you mix up and store large batches for some time in recirculating systems for use in your larval culture attempts.

Larval settlement and metamorphosis:

After all is said and done, the final step in larval culture is to encourage the competent larvae to settle and metamorphose into the adult body form. Just as a caterpillar chooses a place to form a cocoon and metamorphose into a butterfly, the tiny free-swimming larvae of marine invertebrates must choose a place to settle and metamorphose into the adult body form. Unlike a butterfly, however, many marine invertebrates are attached to the reef surfaces, and they do not have any chance to move after metamorphosis if they made a bad initial decision of where to settle. Therefore, the larvae of most marine invertebrates appear to be very choosy in where they decide to settle down, attach themselves and metamorphose into an adult.

Unfortunately, larval settlement is a topic about which scientists still know very little, and despite more than 50 years of active research in the area, we still lack a good understanding of the chemical compounds that induce larval settlement for all but a couple of marine invertebrates. To date, there is no single species kept in home aquaria for which there is not some controversy about the nature of the cues to which larvae respond during settlement and metamorphosis. Sadly, there are still a large number of marine species for which there is currently little hope for successful culture, because even if we manage to figure out how to feed and raise the larvae, we know nothing about their settlement requirements. Many home breeders and researchers alike have spent countless hours raising their larvae only to watch them die in culture because they can’t figure out the cues necessary to induce larvae to settle.

Larvae are said to be competent when they become capable of settling (and metamorphosing) if provided with the appropriate cue. If you have good culture techniques, and you see that larvae are not growing despite appearing healthy (competent larvae typically reach a given size and then keep the status quo), it is likely that your larvae are competent but have not yet been provided with the appropriate cue to metamorphose. Sadly, the only answer at this point is trial-and-error until someone discovers the cues larvae require to accept a given place as an appropriate one for settling. That is certainly not to say that this is a futile exercise, but it is something that everyone who decides to attempt captive culture should be aware of and prepare for – think about the possible cues larvae may use to locate suitable habitat and try to expose the competent larvae to everything you can think of (such as algae or prey species suitable for the juveniles, or live rock from the habitat in which you would be most likely to find the animals). This does not guarantee success, and I have personally raised several species of nudibranchs only to have the larvae remain in culture until they begin to die as I try desperately to give them everything I could think of to settle on, but is the first step in discovering the cues necessary to elicit settlement of competent larvae. Besides, if no one tries to find the cues necessary for inducing settlement of these species, they may never be raised successfully in captivity.

Regardless of the actual cue that larvae respond to, most studies of larval settlement have shown that larvae of most sessile reef species must also be presented with a hard surface coated by a natural bacterial film before they will attach and metamorphose. Provided that you have some small chunks of live rock (or some artificial facsimile that has been allowed to develop a bacterial film in a reef tank for a couple of weeks) on which you are trying to illicit settlement, there are a couple of ways to cheat on forcing larvae to settle. Perhaps the easiest is that many species of marine invertebrates respond to a dose of potassium chloride (KCl) by settling and metamorphosing normally. This is a delicate matter however, because in almost every species tested to date, there is a bell-shaped response of larvae to excess potassium exposure: high levels of KCl are just as ineffective as very low doses at inducing larval settlement. Although the effective levels of excess potassium vary greatly by species, in general levels on the order of 5 - 25 mM excess K+ is usually sufficient to induce larval settlement. If you’re not sure about how to calculate the dose for your culture application, I’d advise you to check an introductory Chemistry text for the calculations. Again, I encourage interested readers to check the database of the Breeder’s Registry for any information about settlement cues tried by others and what has or has not worked in this regard before getting into the trial-and-error phase on your own. And if you do try, please take the time to report your findings to the Breeder’s Registry and help the database to grow so that future attempts at breeding can benefit from your experiences.

I hope that this brief overview is sufficient to encourage more people to consider home culture attempts. If the number of hobbyists culturing these animals at home increases, it can only help both those interested in the continuation of the hobby and the conservation of natural reef communities. I look forward to the time that captive culture begins to meet most of the demand for reef animals in home aquaria, and encourage every serious hobbyist to give it a try!

Useful References:

Cripe, D. (1999). Algae Nutrition. The Breeder’s Registry, Journal of Maquaculture 7(3): 57-64.

Hoff, F. (1996). Conditioning, Spawning & Rearing of Fish, with and Emphasis on Marine Clownfish. Dade City, FL, Florida AquaFarms, Inc.

Hoff, F. and T. Snell (1999). Plankton Culture Manual. Dade City, FL, Florida AquaFarms, Inc.

Jaeckle, W. (1995). Variation in size, energy content, and biochemical composition of invertebrate eggs: correlates to the mode of larval development. In: L. McEdward (ed) Ecology of Marine Invertebrate Larvae. CRC Press, Inc., Boca Raton, FL.

Levin, L. and T. Bridges. (1995). Pattern and Diversity in Reproduction and Development. In: L. McEdward (ed) Ecology of Marine Invertebrate Larvae. CRC Press, Inc., Boca Raton, FL.

Moe, M.A. Jr. (1982). (revised 1992) The Marine Aquarium Handbook - Beginner to Breeder. Green Turtle Publications, Plantation, FL.

Moe, M. (1997). Breeding the Orchid Dottyback, Pseudochromis fridmani: An Aquarist's Journal. Plantation, FL, Green Turtle Publications.

Moran, A. (1999). Size and performance of juvenile marine invertebrates: Potential contrasts between intertidal and subtidal benthic habitats. American Zoologist 39:304-312.

Strathmann, M. (1987). Reproduction and Development of Marine Invertebrates of the Northern Pacific Coast: Data and Methods for the Study of Eggs, Embryos, and Larvae. University of Washington Press, Seattle, USA.

Toonen, R. 1998. Green Water: The Culture of Marine Phytoplankton. Reef Aquarium Farming News 13:2, Jan. (http://www.garf.org/news13p2.html).

Toonen, R. 1996-1997. Invertebrate Culture, Parts 1-4. The Breeder’s Registry, Journal of Maquaculture 4(4):6-31, 5(1):4-13, 5(2):31-37, 5(3):41-51.

Wilkerson, J. D. (1998). Clownfishes: A Guide to Their Captive Care, Breeding & Natural History. Shelburne, VT, Microcosm.

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