Introduction
The genus Amphiprion is a group of saltwater fish housing most of the common clownfish available to marine hobbyists. The genus consists of approximately twenty-nine recognized species. The subfamily (Amphiprioninae) housing Amphiprion also contains the genus Premnas, to which the only other ‘common’ clownfish species (Premnas biaculeatus, the maroon or spine-cheeked clownfish)
belongs.
The genus Amphiprion is found in shallow, warm water throughout the Indian and Pacific Oceans and in the Red Sea. Species distribution tends to be fairly small; this is likely due in part to their breeding strategy and limited mobility. In nature, they will relate to a single anemone, spending their time in very close proximity to the stinging tentacles of the anemone, to which they are either immune or have adapted to not trigger a stinging response (there are several theories regarding how they live safely within the tentacles). Removing the host anemone of a wild clownfish will leave the fish
vulnerable to predation and typically proves deadly. Fortunately, the anemone hosts are not needed for clownfish in the safety of aquariums and they do very well in tanks without them.
Most marine species, clownfish included, have a period during which they naturally drift among plankton in nature. During this time they are at the mercy of the ocean’s currents and are restricted
to eating other planktonic animals. The length of this planktonic stage is, in many cases, related to the difficulty of raising marine fish, with those having a shorter planktonic stage being, in general, easier
to raise. Clownfish have a short planktonic stage, usually lasting between one and a half to two weeks. After this planktonic stage the fry ‘settle’ out of the open water and begin to relate to
structure.
Clownfish Gender
Clownfish, like many other marine fish, change gender at different stages throughout their lives. Most clownfish are born without a determined gender, and are able to remain gender neutral throughout
their life, in some cases. Typically, a group of young fish will settle on a single anemone and the two most dominant fish will mature into a breeding pair. The most dominant will become a mature
female, which will be larger than the rest of the group, and the second most dominant will become a mature male. The remaining fish will remain in an immature state. If the mature female dies, the
male will often mature into a female and one of the immature animals in the group will mature to take his place. This structure (immature to male to female) is known as protandrous
hermaphroditism and is the gender pattern of most Amphiprion species, including A. ocellaris.
Ocellaris Clownfish
Amphiprion ocellaris, commonly known as the ocellaris or false percula clown, is one of the more common clownfish species in the marine hobby. It is also said to be one of the easiest to breed, and
my experiences are consistent with that. The body of the fish is bright orange and there are several (usually three) vertical white stripes on the body that are outlined with thin, black margins. There
are many color patterns that have been selectively bred for the marine hobby. These include nearly solid orange, white, or black, and many variations and patterns with each base color. There have
also been breedings of ‘balloon’ types and long-finned varieties, although these don’t seem to be popular at this time.
The ocellaris clown stays relatively small with males reaching around 2” and females around 2.75” – 3”. All clownfish are relatively poor swimmers and relate very strongly to a single piece of structure
in an aquarium. The ocellaris clowns are notable for being even worse swimmers than most; swimming is accomplished by ‘wagging’ the back half of the body and the pectoral fins and is
comical to watch.
Housing
My breeder clownfish were housed in 20 gallon (long) tanks with bare bottoms and minimal decoration. Each tank held two 8” by 8” ceramic tiles, one flat on the bottom and the other angled up
to the side of the tank (at approximately 45°). Each tank also contained a 6” terra cotta flower pot that was laid on its side. The breeding tank for the ocellaris contained one mature female, one
mature male, and one immature fish. The immature fish was largely ignored except when the adult pair was tending eggs, at which time it was kept away from the nest, but not bullied if it remained on
the far side of the tank.
The breeding tank was part of a rack of eight tanks that were plumbed together. The system had a 90 gallon sump that housed a multi-stage filter system and the life support equipment for the
system (circulation pumps, heaters, protein skimmer, etc.). The water was maintained at 80° with moderate water-flow and a salinity of 35 ppt (1.023 specific gravity) and a pH of 8.2. Water changes
of approximately 25% were performed once a week and evaporation was topped off at least twice per week.
The rack had a (two bulb, four foot) shop-light mounted above the top row of tanks that was on for 12 hours per day (continuous). The rack also had blue LED rope-type lights strung over both rows of
tanks. The LED lights were on from about one hour prior to the main lights going out until about one hour after they came back on in the morning. I didn’t do extensive testing to confirm this but,
anecdotally, there seems to be a connection to the reverse photoperiod and breeding, as I never got viable eggs when the blue lights were not on all night, even if I turned them off during a time when
the adults were breeding very regularly.
Feeding
The adults greedily accepted virtually any food offered. The maintenance diet was a mixture of seafood that had been grated. This mixture included shrimp, clams, various white fish, and
occasionally scallops (if they were found on sale!). The mixture was soaked in a vitamin supplement prior to feeding. The adults also regularly got frozen Mysis, brine shrimp, beefheart,
bloodworms, and capelin eggs in addition to pellet, flake, and gel foods and anything that happened to flow into the tank from the sump (occasional copepods and amphipods mostly). In
short, the adults eat virtually anything that is edible to a fish, and likely some things that aren’t!
The fry are a completely different story. When they hatch they are very small and will typically only respond to live foods. They are also poorly developed and have little in the way of fat
stores, meaning they must be able to eat often and with little effort. Volumes could be (and have been) written about feeding larval marine fish. I fed mine with a steady supply of rotifers
for the first week and then transitioned them to baby brine shrimp. Some breeders start them on newly hatched small strain (San Francisco Bay origin) baby brine shrimp (bbs), which will give
a much lower success rate in many cases but is also much easier (and when you start with 2000 eggs a low success rate is not a huge problem). After 10-14 days the fry will begin to feed on
more variety, easily transitioning to non-living foods.
Breeding
When I started keeping fish, in the mid 1980’s, marine fish were still considered basically impossible to successfully breed in captivity. Fortunately this is no longer the case and many species are bred both
by hobbyists and on a commercial scale. The fact of the matter is that some, clownfish included, were easy to breed but we simply didn’t know the secrets to raising fry. That said, clownfish are actually
easy to get to breed, but there is a learning curve to raising the fry. The adults breed much like substrate spawning cichlids (think convicts of the ocean). They carefully clean a flat, hard surface with
their mouths then make alternating passes with the female laying rows of eggs and the male fertilizing them. The eggs are very small (just over 1mm) but numerous. My spawns averaged around 1000 to
1200 eggs, but spawns up to around 2000 eggs are regularly reported.
After the eggs are laid, the parents will guard them until they hatch. During incubation, the eggs are fanned by one of the parents (usually the male) while the other defends the territory. When the eggs
hatch, there is no further parental care exhibited. The eggs will hatch at night and will turn silver in color the day of hatching. When the eggs turned
silver in my tanks, I would remove the spawning surface and place it in a 5.5 gallon tank that was filled with water from the breeding system. The 5.5 gallon tank contained a heater and several airstones
that provided gentle, but constant, circulation. The tanks were wrapped in black plastic to eliminate light entering from the sides as there is evidence that the fry orient towards light and, if it is coming in
from the sides, it can confuse them. The fry tanks were given water changes of approximately 2 gallons, twice per day, with the replacement water coming from the breeding system. The fry were
kept in these tanks until they settled, at which time they were divided and placed in 10 gallon tanks, with approximately 75 fry per tank.
The eggs hatch in around 10 days (at 80°) and the fry are small (around 3mm) and poorly developed. They stay in the water column and swim in short bursts. They don’t store much energy and must eat regularly, with it being important to have a high density of prey items so they don’t need to swim far to get their next meal. Fry As mentioned previously, the fry of clownfish go through a planktonic stage that lasts approximately ten days. During this time, the fry grow rapidly and most breeders cycle them through several different food items before they settle out. As mentioned earlier, some
breeders start clownfish fry on small strain bbs. These breeders often experience heavy losses for the first couple of days, but still end up with a large number of fry.
My fry were not started on bbs. Instead, I made the decision to culture rotifers and micro algae. There is a great deal of information available on culturing these and it is beyond the scope of
this paper to explore this. I fed rotifers to the fry for the first 3 days, maintaining a high density of them in the tanks. After 3 days, I started introducing small strain bbs while continuing to feed
rotifers until it looked like all fry were eating bbs (usually around day 5). Around day 7, I started introducing normal strain bbs, feeding this until the fry settled. After settlement, I transitioned
the fry to finely ground flake food and pellets while still giving 1 daily feeding of bbs. The fry continued to grow quickly, reaching around 1” in 5 weeks or so.
Conclusion
Clownfish are, in my opinion, easier to induce to spawn than many of the substrate spawning cichlids with which they share several breeding characteristics. The adults will clean a surface
and protect the spawn until hatching, pair bonds are strong, and the adults zealously defend their territory. The fry are not easy to spawn, but they are certainly among the easiest of the
marine fish. The difficulty of raising clownfish fry lasts less than 2 weeks in most cases and, after that stage, they are as easy to raise as common substrate spawning cichlids. They are certainly a
challenge, but they are also one that most experienced fish breeders should be able to complete, and it is quite a rewarding experience.
