A breeder tank is a fish tank that is set up to encourage breeding among fish species and has a safe environment that protects fish fry as they grow. The breeder tank has accessories that allow pregnant female fish to give birth without being hassled by male fish. Fish fry either migrate to a nursery tank compartment or hide among marine plants designed to provide cover from predatory fish.
Fish tank owners can set up a breeder tank by selecting a floating nursery that features two or more compartments that separate pregnant females, males and fish fry from each other. Pregnant fish are scooped up with a net and transferred into the breeder, where they give birth to live babies. The babies swim through holes into a bottom compartment, where they live until they grow large enough to be transferred to the main tank. Without this protection, fish fry are eaten by adult fish.
Some fish species lay eggs, which are scattered about as the pregnant fish swims. To protect the eggs, tank owners add one or more leafy plants to the tank. The eggs adhere to the plant leaves. When hatched, the fish fry easily hide among those same leaves. Young fish are further protected by removing the plants to a separate tank before hatching.