Clown and Anemonefish

When I first got into saltwater and even now, the Clownfish or Anemonefish have fascinated me. Fishes of the genus Amphiprion and Premnas comprise a group commonly referred to as anemonefishes because of their symbiotic relationship with several genus’ of anemones. They are also called clownfish because of their bright colors and bobbing swimming habits.

Whether you call them anemonefish or clownfish, they enjoy a universal popularity among marine aquarists. They represent an excellent choice for your first spawning and rearing efforts before you graduate to more difficult species.

The genus Amphiprion presently has 27 identified species. The genus Premnas has but a single recognized species Premnas biaculeatus, more commonly known as the maroon anemonefish. All species of clownfish are found in Indo-Pacific waters. There are no clownfish in the Atlantic or Caribbean.

Anemonefishes do not require an elaborate system to maintain them in good health. For most species a 20-gallon aquarium is adequate and some professional breeders maintain broodstock pairs in 10-gallon aquariums. It is common to maintain a spawning pair in a “community tank”, although due to aggression is it not advisable to keep multiple pairs, even of different species in the same tank, unless it is a tank of large volumes of water. The physical surface and substrate area is more critical than tank volume. In the wild anenomefishes territories are not large in comparison to other damselfishes and this may be a contributing factor to their success in aquariums.
In the wild the clownfish use the anemones for protection against predators and have even developed a symbiotic relationship with their host anemone. The anemone does not sting the fish and the clownfish bring food morsels back for the anemone.

In aquariums the threat of predators is eliminated. This removal of predators makes it unnecessary to keep the anemonefishes with a host anemone. Anemones are much more difficult to maintain than clownfish and have more rigid requirements such as lighting. Lighting is a key requirement in the success of keeping an anemone. They also represent an increased bio-load on the system. If you must keep an anemone with the anenomefishes, realize that this will place additional requirements and demands on the system. Anemonefishes will spawn in captivity in the absence of an anemone.

Lighting requirements are not critical for clownfish provided that a light and dark period be provided. A period of 14 hours of light and 10 hours of darkness is a common practice. Spectrum and intensity may be a consideration if the aquarium contains organisms from high light environments or if you are experiencing blooms of undesirable algae or cyanobacteria. Filtration should be adequate to maintain ammonia/ammonium and nitrate levels at below detectable levels. Nitrates appear to be tolerated by the adults but it has been suggested that elevated levels of Nitrate may interfere with larval development, contributing to low hatchability, and could be a contributing factor to striping variations. Water movement should be adequate to support the filtration system and provide for good CO2-Oxygen exchange.

A suitable spawning site can be the surface of a rock, the glass, a clay flower pot, a short section of 3” or 4” PVC pipe, color does not seem to matter, a ceramic tile, and even the side of nearby powerhead! Initially it may be advisable to provide several possible places available for spawning and once the pair has selected a site remove the others. Unless disturbed, the pair will continue to spawn on the same site.
Once you have decided on a species, you must seek out a potential pair. Amphiprion. ocellaris and Amphiprion perculae are good first choices. These species are relatively small and less aggressive than some of the other anemonefish. There is no compelling reason that I can think of why the other species would be poor choices, except perhaps with the exception of Amphiprion latezonatus, which comes from slightly cooler waters and seems to do best with temperatures of 75° F.

There are several methods of obtaining a breeding pair.
1. Purchase a “proven” pair from another aquarist. Proven meaning that the pair has been observed to spawn. Proven pairs will typically command the highest dollar and if you are purchasing from a breeder, find out why they are selling their broodstock. If it is an older pair, it might be advisable to continue your quest for a younger pair.
2. Purchase a “pair” from a wholesaler or retailer. Unfortunately, these are pairs made by humans, rather than a pair collected from the wild. Often if a large and a small fish seem compatible they may be offered as a pair.
3. Purchase individual fish, introducing a large fish and a small fish together into an aquarium. Watch for aggression and separate if one the smaller fish is constantly being chased and nipped at. This method is generally successful. It may be some time before the fish become sexually mature and begin spawning.

The acquisition of a “proven” pair is no guarantee that the aquarist will be immediately rewarded with a nest of eggs by the anemonefish. It has been commonly reported that the disruption of moving the fish can interrupt even the most “regular” spawners. How long is difficult to predict, but 6 months would not be uncommon.
It is important to introduce a variety of foods once you have established a pair. A variety will improve the overall nutrition of the diet. Broodstock must be in top condition in order to produce spawns with high hatchability and survival rates. Broodstock should generally be fed a minimum of twice per day and some breeders feed four times per day!

I am personally fond of purchasing fresh/frozen seafood at the supermarket. I vary my purchases depending on what’s on sale, so I offer a variety of flavors. Prawns, oysters, mussels, squid, smelt, octopus, and clams are typically used. I will also add dried seaweed (Nori) and supplements on occasion, such as vitamins. Prawns, mussels, oysters, and clams are shelled and cut into smaller pieces and mixed with the other seafood. The mixture is placed in a seal able freezer-safe plastic container that is allowed to freeze (in the freezer) into a solid block. It takes in excess of 24 hours to freeze solid enough so it will not come apart when you grate it, so prepare it well in advance of when you will need it. Feedings are accomplished by allowing the frozen block to slightly thaw (about 20 minutes.) The block is then grated using a cheese grater until the desired amount of food is ready to be fed. The grating method provides various sized morsels. The frozen block, being a mixture allows for a constantly varying diet. I will occasionally feed spirulina flake food.

There are a variety of prepared foods available. Some are quite excellent, however, all manufacturers do not practice a “truth in labeling” and you are feeding unnecessary “fillers” to your broodstock, so some caution is advisable. Regardless of whether you prepare your own feeds or by commercially available products, variety is the key to good nutrition and success.

The long awaited spawning will be preceded with a change in the behavior of one or both of the pairs, although the male is commonly the first to be observed with a change in behavior. This may be increased swimming in the vicinity of the spawning site, nipping at fins and chasing each other, active cleaning of the spawning site, moving of substrate and rocks. It never ceases to amaze me how such a small fish can manage to move a sizable rock to the other side of the aquarium.

The female will become more full in the abdomen and the breeding tube will become extended and visible. Egg laying has been reported happening at all times of the day and some aquarists have indicated that it has occurred during darkness. My experience that once a pair begins spawning with any regularity they will generally spawn at the same time of day every time. The female lays the adhesive eggs at the selected site and then the male fertilizes them.

Egg masses vary in size and quantity, depending upon the species. Amphiprion ocellaris may only lay 300 to 500 eggs per spawning while Premnas biaculeatus commonly lays 1500 to 2000 eggs! Eggs are small slightly oval masses generally 1 to 2 mm in length. Coloration is generally pink to orange. A yellowish color may indicate a dietary deficiency in the adults’ diet.

Incubation periods vary between the species and water temperature also affects development, but typically the eggs will hatch on the 6th to 10th night after the eggs were laid. The eggs undergo several distinct color changes as they develop; the eyes are usually visible by day 3 or 4 followed by a change in overall darkening of the coloration to an orange-tan purple, followed by a silver/quicksilver color just prior to hatching. The exact coloration may vary, but the silver/quicksilver coloration with distinctly visible eyes is usually a good indicator that the eggs will hatch within a night or two.

The aquarist need do little during this time, as the adults will care for the eggs, constantly guarding, fanning, and removing undeveloped eggs. Occasionally the adults may eat the eggs. This is not uncommon with newly spawning pairs. Generally this behavior abates after several spawns, but in some instances it may be necessary to separate the pair and re-pair with other fish. During the incubation, feed normally and avoid disturbing the pair or the system (not a good time for a thorough cleaning, although some have reported that the pair seemed unconcerned with major activity by the aquarist. Each pair tends to be different.

The eggs typically hatch within two hours of the onset of darkness. The aquarist must be prepared for this event and should have a separate rearing tank ready to receive the larvae. A ten or twenty gallon aquarium is adequate for this purpose. I have successfully reared 30 to 50 larvae through metamorphosis stage to 30 days in a 2-½ gallon “fishbowl” before needing to transfer the juveniles to a larger vessel. The sides should be “blacked out”, either by painting the outside of the glass black or covering with black plastic or paper. There is some disagreement as to the bottom of the tank; some recommend a white bottom so that cleaning is easier. Others recommend a black bottom so that the food organisms are easier for the larvae to see. I have no opinion on this and opt for black simply to avoid needing two colors of paint.

Water from the parents’ tank is preferable and should be used at first. If using a small aquarium, I would recommend only filling it with five gallons initially (I’ll explain why later on). If you need a submersible heater to the maintain temperature the same as the adult tank, use a heater guard and cover the pilot light with electrical tape. The larvae are phototaxic meaning they are attracted to light. They are not strong swimmers during the first week and there have been numerous reports of finding dead larvae in the vicinity of the heater (apparently attracted by the light and killed by the hot water surrounding the heater). If you can avoid it don’t use a heater. An air source with a length of rigid tubing to provide circulation and improve gas exchange at the surface, don’t use an airstone until later on. A light source sufficient to illuminate the area and a timer to control the light period should also be provided. Some people leave the lights on 24 hours the first few days, however, I have used a 14 hour light / 10 hour dark cycle with good success.

You will need to have your rotifer and greenwater cultures established otherwise your efforts would be very disappointing.

Now you await the moment of hatching with a small bowl/dish and a flashlight. Newly hatched larvae are quite small (1 to 2 mm), relatively transparent except for a very small yolk sac and reflective eyes. Once you detect that hatching has begun, turn off the tank filtration, unless of course you want to lose the hatch to your filter! I use a “mini-mag” flashlight that I manage to tape to the side of the aquarium in a corner so that it shines into the tank just below the waterline.

The larvae will swim towards the light and can be collected by dipping the bowl into the water so that they are pulled into the bowl as it fills. The contents of the bowl are then transferred gently to the rearing tank. I think everyone should experience the joy of standing over a tank in the dark for several hours while trying patiently to capture every last larvae! Once you have accomplished this task, turn off the flashlight, turn the filtration system back on in the adult tank and get some sleep. The yolk sac provides an initial reserve and they will not need to be fed just yet. Although some aquarist stock/inoculate the rearing tank with rotifers and greenwater prior to transferring larvae you can wait until the next day to do so.
The larvae do best on an initial diet of rotifers and the general rule of thumb is that the larvae should not need to swim more than one body length in order to feed. What this means is you need lots and lots of rotifers. This is also why I recommended starting with a smaller volume of water in your rearing tank (as opposed to filling it up). The rotifers must be fed so as to be nutritional for the larvae. Greenwater is commonly added to the rearing tank so that the rotifers will have a food source. Additionally, the alga cells can make use of some of the nitrogenous compounds from the larvae waste.

Water changes are a necessity. Unless one is changing 100% of the water, which is neither practical, nor a good idea, a water change represents a dilution of the pollutants. Dilution will never eliminate the pollutants. You can remove a portion of the water and replace it with “clean” water, or add more water and increase the overall volume. Either way the effect is the same; the pollutant levels have been reduced. By starting with five gallons in your rearing tank, you can add one gallon daily and essentially have the same results as a water change. The advantage is that this method eliminates the possibility of removing larvae while siphoning out water and you are slowly increasing the volume to allow for growth and reduce overcrowding. You will need to make allowances when feeding for the increased volume. By the time the tank is full, larvae should be both large enough and strong enough swimmers to avoid the siphon tube.

Rotifers should be fed for the first 10 to 14 days. Metamorphosis occurs anywhere from six to ten days. Metamorphosis is when the larvae change to juveniles. They undergo some distinct physical changes and look more like clownfish. This is a crucial time and good nutrition and water quality will help to decrease the mortality rate. Newly hatched brine shrimp should be introduced at about day seven and ideally not be offered for more than ten days. Rotifers can be discontinued when you observe that the juveniles are all able to feed on the brine shrimp. After five days of feeding brine shrimp begin introducing prepared foods and discontinue feeding brine shrimp as soon as the juveniles accept the prepared foods.

Once metamorphosis has taken place replace the rigid airline with a foam filter. Depending on the number of anemonefish you have successfully reared, you may need to move them to a larger tank in order to reduce losses due to aggression and to insure that all of the fish are getting enough to eat for good growth. A size of generally one-inch size in four to six months is a reasonable to expect.

References:
Fautine, Daphne G. & Allen, Gerald, R., 1994, Anemonefishes and their Host Sea Anemones, Tetra Press, Germany.Moe, Martin Jr., A., 1989, The Marine Aquarium Reference: Systems and Invertebrates, Green Turtle Publications, USAWilkerson, Joyce D., 1998, Clownfishes: A Guide to their Captive Care, Breeding & Natural History; Microcosm Ltd., USA