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Book Excerpt: Clownfishes and other Damselfishes

Clownfishes and Other Damselfishes: The Complete Guide to the Successful Care and Breeding of These Hardy and Popular Marine Fish

Book Excerpt: Clownfishes and other Damselfishes
The Complete Guide to the Successful Care and Breeding of These Hardy and Popular Marine Fish

Jeff Kurtz

Pomacentrids purchased in good health are about as bulletproof as aquarium fishes can get. But the operative phrase here is “purchased in good health.” Unfortunately, these fishes may endure a lot of stress from the time they’re captured in the wild until they appear for sale at your local fish store. As a result, when many specimens reach your dealer’s shop they may be on the verge of succumbing to disease, injury, ammonia poisoning, or other stressors associated with collection and shipping.

Chapter 3: Choosing and Housing Pomacentrids

Signs of a Healthy, Happy Pomacentrid

A healthy pomacentrid will have a full, robust body with completely intact fins, vibrant coloration, and clear, non-bulging eyes. It should be swimming actively (though clumsily in the case of clownfishes) and behaving boldly. Most importantly, make sure the specimen is eating as it should. It is seldom difficult to elicit a feeding response from a healthy pomacentrid, so be sure to ask your dealer to feed the specimen right in front of you. If it doesn’t eat, pass it by. Period.

Avoid specimens that are listless and lethargic; cowering in the corner of the tank; twitching, trembling, or dashing about nervously; swimming erratically; breathing rapidly; or scraping their bodies against rocks, decorations, or other objects in the tank. Also avoid any specimen that exhibits faded coloration; any obvious injuries, pits, or lesions; ragged, torn, or rotting fins; excessive body slime; a velvety coating or tiny white spots; cloudy or bulging eyes; or a pinched-in belly. Essentially, if any physical or behavioral symptom gives you cause for concern, you’re better off bypassing the fish that exhibits them.

And don’t limit your health evaluation strictly to the specimen you want to buy. It’s important to pay attention to the condition of the other fishes that are sharing its tank, too. If you see other specimens in the same tank that are sick, dying, or dead, it’s a pretty safe bet that it won’t be long before the specimen you’ve got your eye on gets sick as well—even if it appears to be perfectly healthy at the moment.

A. ocellaris are tank-raised in large numbers for the aquarium hobby. This one has an abnormal pattern.

When selecting pomacentrids for your tank, pass over any that are lethargic, hiding, or uninterested in food.

Patience Is a Virtue When Purchasing Pomacentrids

Pomacentrids that spend a few days in a dealer’s tank getting acclimated to aquarium conditions and getting accustomed to eating standard aquarium fare before they are purchased tend to have a much better overall survival rate. So do yourself a favor and resist the urge to buy that damsel or clownfish on the same day it arrives. If you’re concerned that another customer will buy the specimen you want in the meantime, ask the dealer whether you can put down a little earnest money to hold the specimen for a few days so you can be sure it’s healthy.

Resist Those Tiny Discount Damsels!

It’s quite common for aquarium stores to offer very small damselfishes for sale at just a few dollars apiece. While these prices may seem like an excellent deal, those tiny discount damsels are really not such a hot bargain, after all—a truth that I had to learn the hard way.

Some years ago I was stocking a new marine aquarium and decided that a school of six blue-green chromis, Chromis viridis, would be a great way to introduce some activity and color to the tank. Imagine my delight when I discovered that a dealer in my area was offering blue-green chromis for the low, low price of just $1.99 each. They had just arrived that day, and I was first in line to buy them! How could I resist? Sure, they were only about a half inch (1 cm) in length, but they would grow, right? Besides, the larger specimens in an adjacent tank cost twice as much!

I took my six specimens home and acclimated them very gradually to my quarantine tank, still smug about my substantial dollar savings. The folly of my purchase started to become apparent the next morning when I found one of them dead. No problem, I thought to myself. I’ve got five chromis left—still enough for a small school. The next day, however, I was down to four. The day after that, only two remained. And then, the following morning, there were none.

The lesson I learned from that disappointing loss, one that has been confirmed many times by the experiences of other hobbyists, is that undersized damsels, however desirably priced they may be, have an absolutely abysmal survival rate because they are simply not resilient enough to endure the rigors of capture, shipping, and handling.

Buy Captive-Bred Clownfishes

On the freshwater side of the aquarium hobby, the vast majority of specimens sold on the market are bred commercially. But just the opposite is true on the marine side of the hobby. The number of species that are still wild caught far exceeds the number of those that are captive bred on a commercial scale.

There’s a good reason that so few marine fishes are being bred in captivity. The eggs and tiny larvae of most reef fishes go through a prolonged pelagic stage, during which they drift over many miles of sea with the planktonic rafts. Eventually they reach a stage of development at which they are ready to settle on a coral reef.

This reproductive strategy has the obvious advantage of distributing a species over a very wide range. But, as you might imagine, it also creates lots of headaches for aspiring breeders because little is known about how to sustain such minuscule larvae during this long pelagic stage. Even culturing a food small enough to fit into the tiny mouths of these larvae is problematic. On the other hand, many of the clownfishes are now being commercially bred on a routine basis.

Captive breeding of clownfishes is easier than it is for many other reef fishes because the clownfishes are demersal spawners (they lay their eggs on a substrate rather than in the water column), the larvae are fairly advanced developmentally when they hatch, and the larvae don’t have as prolonged a pelagic stage as many other reef fishes do. Because clownfish larvae are relatively large, they are able to accept easily cultured live foods, such as marine rotifers and, later, brine shrimp.

Whenever possible, hobbyists interested in purchasing a clownfish should choose captive-bred specimens over wild-caught specimens. This offers numerous benefits to the hobbyist. They include:

• Captive-bred clownfishes have not had to endure the rigors of capture and prolonged shipping, so they are in much better condition overall when they arrive at your local aquarium store.

• Captive-bred specimens are used to life in captivity—the only life they’ve ever known! There is no difficulty getting these fish to accept standard aquarium foods.

• Captive-bred clownfishes are less likely than wild-caught individuals to carry diseases or parasites.

• You can also be confident that you’re starting with a young specimen. There is no way of knowing whether a wild-caught specimen is just starting out in life or approaching the end of its natural lifespan.

Sometimes captive-bred clownfishes cost slightly more than wild-caught specimens, but they are well worth the price! Wouldn’t you rather pay a bit more for a specimen that is far and away more likely to survive in your tank and that wasn’t taken from the wild? Consider it an investment in success.

Deadly Harvest: A Note About Cyanide Collection

One very regrettable aspect of the marine aquarium trade is the ongoing use of cyanide poison to stun and capture reef fishes in some areas, such as the Philippines and Indonesia—and, yes, damselfishes (though, to my knowledge, not clownfishes) are among the fishes known to be collected in this manner from these areas.

Cyanide is used for the very simple reason that it facilitates the easy capture of large numbers of fishes with very minimal effort. The fish collector simply squirts the cyanide mixture into the coral heads and crevices where the fishes take refuge and then gathers them up after they become immobilized and sink to the bottom. Because cyanide collection is so much easier than net collection, fishes taken in this manner can be brought to market at a price that is much more attractive to hobbyists.

The problem is that virtually all cyanide-exposed fish perish—many right there on the spot and many more during transportation and distribution. Those that linger long enough to make it into a hobbyist’s tank die days or weeks later, leaving the hobbyist guessing what he or she could possibly have done wrong to cause the fish’s fatality.

What’s worse, cyanide collection doesn’t kill only fishes. It also wipes out any invertebrates that are exposed to the poison, which can lead to the loss of entire tracts of coral reef.

Unfortunately, there’s no way for the average hobbyist to know just by looking at the fishes in a dealer’s display tanks whether or not they were collected by net or via an unsustainable method such as cyanide poisoning. But there are steps conscientious hobbyists can take to ensure that they aren’t supporting this ecologically devastating practice. They include:

• Get to know the dealers in your area, and ask them about the source of their livestock. Better dealers should be able to tell you where their fishes come from (remember, fishes collected from the Philippines or Indonesia should be considered suspect) and whether or not they were collected in a sustainable manner.

• As mentioned earlier, purchase captive-bred fishes whenever possible. There’s obviously no risk that those specimens have been exposed to cyanide.

• Be willing to pay a few extra dollars for net-collected fishes. An inexpensive fish is no bargain if it dies shortly after purchase.

• If it is available in your area, purchase livestock that has been certified by the Marine Aquarium Council (MAC). MAC certification is your insurance that a fish has been collected, handled, and shipped in a sustainable fashion.

Some collectors use cyanide to catch damsels and other fish, a practice that threatens the survival of coral reefs. Avoid purchasing cyanide-collected fish.

Choosing a Tank for Pomacentrids Is No Big Deal

Having limited space in your home to accommodate an aquarium is not necessarily a limitation on keeping clownfishes and damselfishes. Many are well suited to life in a modest-sized home aquarium in the range of 20 to 40 gallons. Even tanks that would be considered grossly undersized for many other reef fishes can be suitable housing for certain pomacentrid species.

Nice for Some Nanos…

With the burgeoning popularity of nano aquariums—defined for our purposes as systems of 30 gallons or smaller—the demand has risen for marine fishes that can adapt to life in such confined quarters. Many pomacentrids, especially certain smaller clownfish species such as the ocellaris and percula clowns, can be considered reasonable candidates for these smaller systems.

Some of the smaller clownfish, such as ocellaris and percula clowns, will do well in a nano aquarium.

…But Not for All

Not all nano aquariums can realistically support a clownfish or damselfish for the long term. Don’t assume that just because one of these fishes can fit in a very small nano system that it will be healthy and happy there over the course of its life. Pomacentrids can live for well over a decade in captivity, and they deserve the best care we can provide over the course of that long lifespan. So we have to be realistic about the volume of water we attempt to keep them in.

Would a 20- to 30-gallon system suffice for a small to medium-sized pomacentrid, provided it is well maintained and appropriately stocked? Almost certainly. When you move into the 10- to 12-gallon nano range, you’re definitely entering borderline territory, although it could be done with meticulous maintenance and attention to water parameters. But a 5-gallon or smaller system? Consider these out of the question for even the smallest clownfish or damsel.

Nano Negatives

Because so many pomacentrids are good candidates for smaller aquariums, it behooves us to examine some of the drawbacks inherent in these systems. These challenges shouldn’t necessarily be viewed as deal breakers for the aspiring clownfish or damselfish keeper, but understanding that they exist is the first step toward overcoming them.


A smaller volume of water is far less stable than a larger volume in terms of its temperature, pH, specific gravity, etc. Changes for the worse occur much more rapidly in a nano tank than they do in a larger system. If the ambient air temperature shifts markedly upward or downward, the water temperature in a smaller volume of water will change much more rapidly than it will in a larger volume of water. Compare the respective cooling rates of a cup of coffee and a pot of hot water and you’ll get the general idea.

Water Quality

A modest amount of evaporation results in a significant increase in specific gravity in a smaller system. So forgetting to perform a freshwater top-off—even for one day—could cause a precipitous rise in specific gravity and have a very adverse effect on the well-being of the livestock in a nano system.

Additionally, any contaminants, such as soap or lotion on your hands, that are accidentally introduced or additives that are accidentally overdosed are much more concentrated in a smaller volume of water than they are in a larger volume.

Lack of Space

Furthermore, the smaller the aquarium, the easier it is to overstock or stock inappropriately. Giving in to the impulse to add “just one more specimen” can tax the biofilter in a system of any size, but in a small system, yielding to this temptation can have a disastrous impact on water quality.

Also, you have to factor in the relative aggressiveness of many pomacentrids when considering keeping them with other species or conspecifics in very confined spaces. If an aggressive damsel or clownfish takes issue with one of its tankmates (or vice versa) in a 100-gallon aquarium, the two can usually stay out of each other’s way, thereby minimizing territorial squabbles. But throw the two adversaries together in a 20-gallon tank and they’ll fight like two cats in a duffel bag because there’s simply no way for each to escape the other’s line of sight.

Again, this isn’t an attempt to dissuade you from keeping a clownfish or damsel in a smaller system (with the exception of really small nanos, which I would discourage), just to apprise you of the limitations of small systems and the special challenges they present.

Just Right for Reef Tanks

Corals and other sessile invertebrates are the priority in any reef aquarium. The number of fishes is often kept low in order to minimize their impact on water quality, which must be topnotch in a reef system, and any fish specimens that are introduced are chosen for their compatibility with the invertebrates—i.e., they don’t include sessile invertebrates as part of their natural menu and they aren’t heavy polluters. Many clownfishes and damselfishes satisfy these reef-compatibility requirements superbly, being generally small in size, producing minimal waste, and usually being inoffensive to sessile invertebrates.

Of course, there are exceptions to every rule. For example, the big lip damsel, Cheiloprion labiatus, would not be a good candidate for a reef system containing Acropora spp., as it feeds primarily on the polyps of those corals. For another, the bowtie or black damsel, Neoglyphidodon melas, can’t be trusted in a reef system stocked with soft corals, as they compose its natural diet. But most of the commonly sold pomacentrids are generalized omnivores that can be trusted around corals and other sessile invertebrates. If you do your homework by researching the needs of any clownfish or damselfish specimen before you bring it home, you should have no problems in this regard.

All clownfishes are reef-safe in the sense that they won’t nip at or eat polyps; however, as we’ve already touched upon, they may irritate sessile invertebrates that they’ve adopted as surrogate hosts, preventing them from expanding their tissues to receive the light they need to sustain themselves. In some cases this can prove deadly to the invertebrate, so if this behavior is observed and it continues unabated, the offending clownfish will need to be removed from the reef system.

Many of the pomacentrids are good candidates for reef systems, being relatively small fish that won’t eat corals, anemones, or other desirable invertebrates.

The bowtie damsel is one of the species not safe for reef tanks because they will eat soft corals. This is a juvenile; the adults are solid black in color.

Aquascaping the Pomacentrid Aquarium

Whereas some reef fishes demand ample open space for swimming in an aquarium, clownfishes and damselfishes seem to do best when they have lots of structure in which to take refuge. Clownfishes, absent a host anemone or suitable surrogate, will often adopt a small cave or ledge as a safe retreat. Hence a tank containing pomacentrids should be aquascaped to provide lots of nooks, crannies, crevices, and caves.

Gnarled porous live rock is the ideal choice of aquascaping material, as you can stack it in a greater variety of configurations than you can slab-like rocks. You can also join these live rocks together with plastic cable ties or aquarium-safe epoxy or silicone to enhance stability or to create more elaborate aquascaping—such as bridges or overhanging ledges.

Artificial branching stony corals would provide a nice naturalistic setting for species that naturally seek refuge among coral heads, such as the popular humbug damsel, Dascyllus aruanus, and its very similarly patterned cousin, the black-tailed humbug, Dascyllus melanurus.

As far as substrate goes, crushed aragonite or crushed coral is just fine for pomacentrids. Clownfishes and damsels aren’t burrowers, so it’s not necessary to provide them with a deep sand bed (DSB) unless you plan to utilize one for the combined purpose of nitrification and natural nitrate reduction. A substrate depth of 2 inches (5 cm) is more than adequate if you just want the tank to have a naturalistic look. For a DSB, a minimum depth of 4 inches (10 cm) is recommended.

For easier maintenance and to minimize the amount of debris that gets trapped in the substrate, where it can decompose and quickly foul the water, many hobbyists who keep nano systems prefer to use no substrate whatsoever. Or, if they want the naturalistic appearance of a crushed aragonite or coral substrate, they might choose to use a faux substrate by gluing a fine layer of substrate material either to the bottom of the tank or to a sheet of glass or acrylic that has been cut to fit the bottom of the tank.


The Perfect Introduction to Saltwater Aquariums

Not only are many pomacentrids great fish for novice marine aquarium hobbyists, but they’re also a good choice for introducing kids to the responsibilities of marine fish keeping. A smaller aquarium containing a damselfish or, perhaps, a clownfish pair can be set up and maintained with a little parental oversight. After some basic instruction, kids should be able to manage everyday chores, such as feeding, checking the water temperature, and topping off the tank with dechlorinated tap water to compensate for evaporation. Initially, the parents might want to help with some of the more complicated tasks, such as testing for ammonia, nitrite, and nitrate and performing water changes, but even these chores can eventually be learned and mastered by children once they’ve had an opportunity to observe how they are accomplished. Such a family aquarium is a great educational tool that will help strengthen a child’s sense of responsibility—not to mention it may just awaken a lifelong passion for the marine aquarium hobby!

Small Pomacentrids in Big Tanks

Introducing a very small pomacentrid to a very large tank can pose certain husbandry challenges that won’t necessarily present themselves when the specimen is in your quarantine tank. These challenges might include certain dangers that weren’t an issue in quarantine and that are never experienced in nature. For example, a diminutive damsel can easily be swept into the overflow chamber of a wet/dry biofilter or get stuck on the intake of a powerhead. Any such hazards must be blocked or screened off to prevent accidents.

The high level of water movement that is necessary in a large system can also create problems for a small pomacentrid. Constantly struggling against a very powerful current can exhaust a little damsel or clownfish—potentially stressing it to the point of death. Also, feeding small pomacentrids is more of a challenge in a larger system because the brisk water movement can quickly disperse small food items before the damsel or clownfish sees it. To mitigate these potential problems, it’s helpful to provide an area of slack current in the aquarium where the clownfish or damsel can rest and take refuge. To prevent tiny food items from dispersing too quickly, it’s a good idea to temporarily unplug your powerheads and pumps at feeding times.

Excerpted from the book Clownfishes and Other Damselfishes: The Complete Guide to the Successful Care and Breeding of These Hardy and Popular Marine Fish. ISBN 9780793816781; April 2010. ©T.F.H. Publications Inc. Used with permission.

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Posted in Aquatic Books by Tsing Mui on October 21st, 2010 at 6:25 am.

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