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Clownfish Breeding

Some of the easier marine fish to breed in home aquariums, clownfishes make a good first breeding project.

By Article and photos Scott W. Michael

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Aquarium Fish International Magazine
A number of anemonefishes regularly spawn in the home aquarium. In fact, most anemonefish species in the aquarium hobby are now being bred in captivity, and captive-raised anemonefish are readily available to hobbyists. With the availability of larval foods and the products needed to keep these foods alive, it is now easier than ever for the hobbyist to raise anemonefishes. Although it is rarely profitable to do this on a small scale, it can be fun, educational and can lead to a sense of accomplishment when you succeed in raising some fish to saleable size.

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Male clownfish are excellent and protective parents
The male anemonefish is a vigilant parent guarding and tending his eggs. Here a male Clark’s clownfish (Amphiprion clarkii) mouths his eggs to keep them clean of debris and fungus.
Captive bred clownfish are much hardier than their wild-caught counterparts
Tank-raised anemonefishes, such as these cinnamon clownfish (Amphiprion melanopus), are much more durable than their wild-caught counterparts.

Finding Broodstock
Because they are hermaphrodites, it is relatively easy to acquire a heterosexual pair of anemonefishes. Simply place two juveniles into the same aquarium. The most dominant fish typically transforms into a female, while the subordinate will develop functional testes.

If you place more than two individuals in the tank, the specimens lower in the pecking order will remain as nonbreeders. This is a truism unless you have an extra-large aquarium of at least a 135 gallons; more than likely, you will have to remove these other individuals, as the pair is likely to relentlessly pick on them. In some of the smaller species (e.g., ocellaris clownfish, A. ocellaris; percula clownfish, A. percula; pink skunk anemonefish, A. perideraion), adding a group of juveniles will often result in multiple pairs forming. The pairs can then be placed in separate broodstock aquariums — they should not be kept together, unless the aquarium is very large (135 gallons or more).

A note about sex change in anemonefishes. Studies have shown that males may not change into females if conspecifics are not present. Therefore, if you have an individual that has been isolated from members of its own kind for some time, it does not mean that it has developed into a female. It may take the addition of a conspecific for this to occur. One cannot always be sure of what sex an isolated anemonefish is if it is isolated. It may develop functional gonads and become a male, or it may remain sexless (the gamete-producing organs may not mature).

Finding an adult pair can be a more difficult prospect. Some fish stores will acquire and sell anemonefish that were collected as mated pairs. However, wild-caught pairs are usually quite expensive and are more likely to harbor parasites than captive-raised individuals. The best thing to do is to try and “pair up” captive-raised individuals. When attempting to “create” an adult pair, it is usually best to acquire fish that differ in size. More than likely, the large fish will be a female, while the smaller fish may be a subadult or a male (size differences between the sexes does not occur or is not as extreme in some species). It is usually more difficult to introduce a potential pair member into a tank that contains a conspecific. In many cases, the resident fish will attack the newly introduced individual and may even kill it. To prevent this, take the resident fish out of the tank and rearrange the decor. Then introduce both fish simultaneously.

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Female clownfish can deposit as many as 500 eggs per nest
The female tomato clownfish (Amphiprion frenatus) can deposit from 300 to 500 eggs per nest.

If this does not work, place the new fish in a portion of the tank that has been sectioned off with an acrylic divider (there are other types of dividers available, but it is important that the two fish can see each other). Make sure water exchange occurs between the two portions of the tank (they need to smell each other). After a few days, remove the divider and see what happens. Some of the behaviors related to dominance establishment may occur, but if one fish begins biting the other, you will have to separate the fish again. Although it will require more patience, it is easier to purchase two or three juvenile fish, and wait until they mature and change sex.

If the tank environment is right and the adults are well-nourished, it is not unusual for a pair to begin spawning within months. If your pair has not spawned after about eight months, you may want to replace one of the partners. If you have acquired juveniles, wait at least 18 months from when you purchased the fish.

On rare occasions, you may end up with two females, which may behave like a heterosexual pair. One female may even deposit her eggs. If you have a pair of fish that has spawned on a number of occasions, but the eggs are always infertile, then your pair may consist of two females. If this is the case, replace one of the pair members with a smaller fish. Although most pairs will spawn at least once a month, in optimal conditions spawning frequency may double that. In most cases, anemonefishes will spawn 11 months of the year in aquaria. If kept in good health, a pair will spawn for many years (there are reports of a pair continuing to spawn for more than eight years).

Broodstock Aquarium and Diet
One of the most important prerequisites for anemonefish breeding is that the fish “feel” secure. In the wild, the anemone acts as a living, stinging security blanket for these fish. You may want to use an anemone in your aquarium, especially if you are trying to raise those species that are closely tied to their host and the tank has appropriate abiotic parameters to keep the cnidarian healthy.

However, it is possible — and usually more practical — to set up an alternative sanctuary for your broodstock. One way to do this is to create a small pile of rocks with an adequate hiding place for the adults, and lean a ceramic tile against the cairn (the tile will provide a good, movable nesting substrate). Many commercial anemonefish breeders use flowerpots (ceramic or glazed) or pieces of PVC pipe as anemone surrogates (add two so that when one is removed to clean, there is another one present for the fish to hide in).

Make sure these hiding places are large enough for both fish to shelter in. The broodstock aquarium should be placed in a low-traffic area. Also, use a shading material to shield the back and sides of the tank. This will provide the potential parents with an even greater sense of security.

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False Clownfish Eggs
The eyes of the developing false clownfish (Amphiprion ocellaris) eggs can be seen in these 8-day-old eggs.
Male Percula Clownfish
A popular favorite with marine hobbyists, the percula clownfish (Amphiprion percula) may take nine to 15 months from hatching to reach sexual maturity. This is a male with his eggs.
Pink Skunk Clownfish
Young captive-bred anemonefishes, such as these 3-month-old pink skunk clownfish (Amphiprion perideraion), will form schools (as seen here). Clownfishes do not exhibit this behavior in the wild.

As far as the environmental parameters and anemonefish spawning are concerned, these fishes are not as particular about water parameters as you might think. They have been reported to spawn over a temperature range of 71 to 88 degrees Fahrenheit, but egg and larval quality are best when spawning occurs at between 79 to 83 degrees. Of course, if you are working with one of the anemonefishes from cooler climates (e.g., wideband anemonefish, Amphiprion latezonatus), you will want to maintain the water at lower temperatures. They have been reported to spawn at salinities of 28 to 35 parts per thousand (ppt) and a pH of 7.8 to 8.3.

Good nutrition is a must if your anemonefishes are going to spawn. The production of gametes (especially eggs) is very exhaustive. The male fish will also burn a lot of calories defending the nest. Not only is a good diet important for “mom and dad,” but it will also affect the health of the eggs and larvae, as well as female fecundity. Therefore, it is important to feed the adult fish three times a day, using one or more nutritionally complete foods available on the market, or you can make your own food (see Hoff, 1996, for a good conditioning food recipe). Some breeders will give their fish an occasional fourth feeding that consists of vitamin-enriched live brine shrimp, fish roe or live zooplankton.

Spawning and Incubation
Most anemonefishes spawn in the middle of the afternoon. Some individuals may abort spawning if disturbed; therefore, it is important to be as inconspicuous as possible when observing a reproduction.

A pair of anemonefish agitated by the aquarist’s presence is more likely to consume the eggs. Other factors that contribute to filial cannibalism include the eggs being infertile or of poor quality. The eggs may also be attacked by fungus or parasites, or the parents may be stressed by tankmates. Inexperienced pairs of anemonefish are also more prone to engaging in filial cannibalism and often cease doing so once they are more “seasoned” spawners. It may take several spawning events before egg-eating ends.

The incubation period of anemonefish eggs differs to some degree between the various species. When maintained at the same temperature, the eggs of Clark’s anemonefish (A. clarkia) usually hatch on the sixth evening after spawning, while those of the dusky anemonefish (A. melanopus) hatch on the ninth evening. Water temperature greatly affects hatching time.

In captivity, hatching usually takes place one or two hours after the lights are turned off and occurs over a time period of 15 to 20 minutes. In some cases, the eggs in a single nest may hatch over a two-day period. There are interspecific differences in the number of eggs that typically hatch in a clutch. Hoff (1996) reports that A. melanopus had a very low hatch percentage, while in A. clarkii it is often very high.

There are two ways to deal with anemonefish eggs: 1) they can be transferred to another tank before they hatch, or 2) the eggs can be left with the parents, and the larvae can be moved to a different tank after hatching. Most hobbyists do the latter, but this method will result in higher larval mortality due to adult predation, predation by other tankmates, death due to mechanical filters or physical damage that occurs when the larvae are transferred.

Hatching the Eggs
Many commercial breeders remove the nest of eggs (which is usually attached to a flowerpot or a piece of ceramic tile) and place it in a different aquarium. The eggs are fairly resilient. As long as the water parameters in the hatching tank are similar to the broodstock aquarium, the eggs should survive the transfer (some authors recommend filling the hatch-out or larval-rearing tank with water from the broodstock aquarium). Simply lift the substrate and the attached eggs out of the water and quickly carry it to the larval tank. In order to replicate the parents’ fanning behavior, an airstone should be positioned near the nest so that a flow of large air bubbles circulates water over the eggs.

Hoff (1996) states that optimal placement of the airstone will result in all the eggs in the nest being agitated by the rising air bubbles but not directly in contact with them. He suggests that if the bubbles continuously pummel the nest, egg mortality is more likely. However, Wilkens (1998) reports that the eggs are usually not harmed as a result of bubble contact.

If you leave the eggs in the tank, remember also that when a pair of fish has eggs, they will be especially aggressive, often relentlessly attacking tankmates. This will result in excessive caloric expenditure to the adult fish and may even cause them to eat their eggs.

Remove the larvae as soon as possible after the hatch. The larvae are phototropic (i.e., attracted to light) and thus can be easily removed from the aquarium after they hatch by placing a bright light source (e.g., flashlight) at one corner of the aquarium. Once the larvae concentrate in that area, carefully scoop them out with a Tupperware bowl or siphon them out with some large-diameter plastic tubing. Never use a net because it can cause fatal injuries to the delicate larvae.

Raising the Larvae
Once the eggs hatch, the hard work begins. It is important to provide the larvae with a healthy, stable environment. This means frequent water exchanges to keep the water pollutant-free. A significant water change (20 to 30 percent of the tank volume) will be required once a day, and you will need to remove detritus from the aquarium bottom at least every other day.

Feeding the larvae is the biggest challenge most fish breeders face (this is also where sources like Hoff, 1996, and Wilkens, 1998, will come in very handy). Live rotifers that have been fed phytoplankton (“green water”) to increase their nutrient value are used from day one to 10. To ensure the larvae encounter enough prey items, the rotifer density should be from 5 to 15 per mL of water. Problems can arise if rotifer densities get too high and the larvae eat too much. Overfeeding can cause depletions in oxygen levels and increase concentrations of nitrogenous wastes.

After the fish are about 6 to 8 days old, you should begin feeding them live baby brine shrimp and pulverized dry foods. Rotifer feeding can end at about 10 to 12 days after hatching, while you can stop feeding newly hatched brine shrimp at about 15 days of age (if you wish, you can continue to feed them Artemia). I should point out that copepods are more nutritionally complete than Artemia, and as a result, the survival of young anemonefishes is much higher when they are fed copepods. Unfortunately, these microcrustaceans are much more difficult to acquire and raise than Artemia. Fifteen days after hatching, the young fish can be fed exclusively on pulverized dry foods. Make sure you feed them nutritionally complete dry food that includes color-enhancing pigments. If larval nutrition is lacking, a number of physical deformities (e.g., missing eyes, deformed jaws, spinal deformities) may result.

From day seven to 15, the larvae of the anemonefishes undergo metamorphosis and settle out of the plankton. At this point, they drop out of the water column and begin spending their time near the aquarium bottom. Besides these behavioral alterations, there are also physical and physiological changes that occur.

Anemonefish breeders will tell you there are several times during development when larval mortality is highest. For reasons unknown, mortality tends to peak two days after hatching and during early metamorphosis (day seven to eight). After this, survival rates are usually fairly high. As for the percentage of hatch, larvae survival also varies between anemonefish species. The easiest species to raise to the post-larval stage are tomato anemonefish (Amphiprion frenatus), percula (A. percula) and ocellaris clownfish (A. ocellaris).

After metamorphosis is completed, and the young fish look like miniatures of the adults, they enter what is referred to as post-larval stage. At this point, the fish are relatively easy to raise. At an age of 15 to 20 days old, aggression can become a problem. Fighting can result in impeded growth rates, damaged mouths, fin abnormalities and death. The best way to reduce aggression problems is to keep the density of juvenile fish high enough to spread out agonistic encounters.

Hoff (1996) reports having fewer aggression problems when the stocking density was at seven to nine fish per gallon. If densities are too high, growth rates will slow down, and more aquarium management will be required. If they are too low, fighting will result (same as with African cichlids). If you can provide an optimal environment, the young fish typically reach saleable size in about four months, but this depends on the food intake, food quality and water quality. They will reach sexual maturity at between 9 to 15 months old.

That ends our anemonefish spawning and rearing primer. For those that want to delve deeper into the topic, I would recommend reading the books in the references list. For those who are serious about commercially raising these fishes, Frank Hoff’s information-packed book is a must. Another great source of information on anemonefish husbandry is the Breeders-Registry (www.breeders-registry.org). Best of luck in all your fish breeding endeavors!

References
Hoff, F.H. 1996. Conditioning, Spawning and Rearing of Fish with Emphasis on Marine Clownfishes. Aquaculture Consultants, Inc. Dade City, Florida. 212 pp.

Wilkens, J.D. 1998. Clownfishes. Microcosm, Shelburne, Vermont. 240 pp.

Wittenrich, M.L. 2008. The Complete Illustrated Breeder’s Guide to Marine Aquarium Fishes. T.F.H. Publications, Neptune City, New Jersey. 304 pp.

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