Breeding triggers:

1. Changes in water temperature, direction of change dependant on species.
2. Changes in water depth, direction of change dependant on species.
3. Changes in feeding, usually increase in live foods.
4. Changes in tank mates, usually separate and re-join male(s) and female(s) or introduce new fish together.
5. Changes in water quality, usually cleaner water of a pH more closely matching that found in the wild for the species of interest.
6. Changes in lighting, usually increase in day length.
7. Changes in tank decor such as the addition of java moss for egg scatterers or small clay flower pots or PVC pipe for cave egg depositors, etc.
8. A healthy ecosystem in the aquarium or pond including a nice growth of algae (for the fish to spawn on and for microorganisms to grow that will feed the fry).

It may take a combination of the above triggers to initiate spawning.

Some species of fish like corydoras catfish are triggered to breed by large water changes (~50%) with slightly cooler (a few degrees F) water. The actual triggers are the decrease in temperature, decrease in water hardness, and cleaner water. Others like goldfish are triggered mostly by light changes (usually coupled with temperature changes as well). As light increases in the spring, they begin breeding. These species may need their light timers changed with the seasons to breed if kept inside. Other fish like danios and live bearers are triggered almost entirely by an increase in water temperature. Labyrinth fish often are triggered to breed by a decrease in water depth. Most fish require a combination of changes to initiate spawning. Each species is different so it is important to know that species' spawning triggers. Another way to initiate spawning is to feed the fish live foods like brine shrimp, tubifex or black worms, daphnia, etc. This mimics the abundance of live foods in spring and also gives the fish the extra nutrition required to produce vast amounts of eggs and sperm. Feeding fish to induce spawning is called conditioning. Often during conditioning, the male(s) and female(s) are separated. When re-joined, they are often ready to spawn.

Separating parents from eggs and/or newborns:

Except in the case of some species of cichlids where the adults protect the young or in a few other cases of unusual fish, the eggs or newborns and their parents should be separated. This not only prevents the parents and other fish from eating the eggs and/or newborns, but also allows more controlled rearing of the young. If you only desire a few offspring, the eggs and/or newborns can be left with the parents. With many species, a few should survive. With others, like zebra danios, the parents will absolutely eat every last newborn they can reach. Fry can be placed in breeding nets until they are larger if only a few are collected. If many are collected, they should be treated as below under fry care.