A tropical fish hatchery is a tank, or larger facility where tropical fish are hatched and allowed to grow in a controlled environment. In the fish-breeding world, tropical fish are those that can live in an aquarium with fresh water, as opposed to marine fish, which need salt water in their aquarium. The hatchery produces larvae for the tropical fish industry. The fish are then sold to individuals with their own fresh water tank systems. A tropical fish hatchery can be a small, indoor operation, and sometimes a series of large outdoor pools.
With constantly filtered and temperature controlled water, fish are able to be hatched year-round. Without hatcheries there would be far fewer tropical fish for sale than are currently available. The smaller hatchery operations need only a few tanks with adequate water flow and filters. The larger facilities will often have tanks for broodstock and spawning, laboratories for genetic manipulation and selective breeding, as well as several staff members to run the delicate operation. Broodstock are a group of mature fish chosen specifically for breeding purposes and to repopulate the tropical fish hatchery.
Certain tropical fish have different spawning and breeding habits. The clownfish, for instance, always spawn late in the afternoon. The eggs are then removed from the spawning tank and placed in another tank away from the parents. It requires at least one hour of darkness for the larvae to hatch and if any light falls on the eggs the remaining larvae will wait until the next period of darkness to hatch.
At this stage the larvae are too tiny to feed on anything larger that minuscule aquatic creatures called rotifers, or wheel animals. The rotifers are spread uniformly into the tropical fish hatchery and the larvae begin to feed immediately. Sustained feeding every two or three hours typically produces the hardiest and most vividly-colored tropical fish. It takes a few days before the juvenile fish are able to feed on brine shrimp, which are minute crustaceans. After a week or so, the tiny fish will usually be ready to begin eating a food made from flaked brine shrimp.
After numerous changes of tank water, the juvenile fish begin to manifest their tropical colors. At this point the stronger and larger fish are transferred to another tank to allow the weaker fish a fair chance to develop. The fish are never moved using a net as this could kill them. They are usually transferred using a cup or bag. There are many details to raising and caring for the eggs and larvae, but these basic steps are common to most tropical fish hatcheries.