Clownfish Fry
(Pre-Metamorphosis)
After hatching, Clownfish are larvae (containing a yolk sack in most cases) and quickly become fry within the first 12-24 hours after hatching. Some eggs hatch with fry having no yolk and babies must start feeding immediately. These fry are often referenced to as skinny young. This condition can occur due to a late hatch or a less than optimal batch of eggs. The fry period often lasts around 14 days, after which fry undergo metamorphosis where they begin drastic physiological changes and begin to resemble their adult parents.
The fry period is when baby clownfish are at their most unstable and is most often the time then young or entire batches die, often with little explanation. A simple error of late feeding in the first couple of days can result is starving clowns and the loss of many young.
Young fry feed almost primarily on small free floating invertebrate during their first 4-5 days (minimum) of life. Most marine fish breeders use live rotifers for food stock as they are capable of rapid division and are small enough for the fry to catch and safely consume. Most fry will not eat prepared food and will starve in the absence of live micro-foods. While it is possible to raise fry with small powdered foods such as fry starter, it runs the risk of fouling the water and not all fry will see it as a viable food source.
Above: Percula Clownfish fry approximately 10 days old.
After 4-5 days, many fry can begin eating freshly hatched baby brine shrimp. Brine shrimp should be fed to fry within a day or two of hatching the brine, as this is when they have their most nutritional value for the clowns and they are small enough to consume. As brine shrimp grow they may become too large for clowns to safely eat, causing fry to choke on meals too large for their mouths, or for brine to do internal damage to clownfish when consumed (characterized by internal bleeding or blood spots near gut). At this stage fry are easier to manage than in the first 5 days but are still vulnerable. While baby brine are much easier to manage than rotifers, they harbor potential risks for fry. Firstly, fry tend to overeat on brine. Brine shrimp offer much more nutritional value than rotifers but they are also bigger. Fry do not know this and eat when possible, resulting in eating until they literally burst in a tank with excess brine shrimp. Secondly, brine shrimp eggs often contain hydroids, or the preforms of jellyfish. Hydroids are the stationary form of a jellyfish where it is attached to a physical surface before becoming free floating. They are characterized by hair like appendages on the glass of a fry tank. Hydroids are lethal to fry and are not usually curable in a fry tank. They will sting fry to death even before they become free floating medusa. The risk of hydroids can be reduced by getting fry to eat powdered food as soon as possible after rotifers. Brine should not be considered a long term feeding solution.
Another shortcoming of feeding brine shrimp is a condition called "Brine Shock". The root cause of this condition seems to be unclear among breeders but seems to be caused by the feeding of brine to young clowns (even after metamorphosis). Brine Shock occurs when young clowns are exposed to stress, resulting in death. For unknown reasons, baby clownfish are less fit to handle stresses while eating brine. Death can occur during tank transfers, from floor vibrations, bumping a tank or even from being spooked by another fish. I have had a group of up to 7 post-metamorphosis fish die at once because one individual caused a panic in a single group. Before doing any transfers of clowns or to minimize accidental loss it is best to reserve brine as a treat after clowns are on prepared foods.