Piranhas are unique creatures that have gained popularity not just because of their appearance, but also because of the many myths that are told about them. Unfortunately only a few species of piranha have been bred, including Serrasalmus nattereri, S. spilopleura, S. gibbus, S. rhombeus. Another that is considered relatively easy to breed is S. maculatus.
Whichever of those species you choose, you should have an aquarium of at least 100 gallons. A group of 5-6 piranhas is quite appropriate; however in the event you want them breeding it is ideal to keep a set only, so that there are no other fish to irritate them. To find a mating pair select two adult piranhas, one thick and the other thinner – in most cases thick piranhas represent females and thinner piranhas represent males. Just be sure you aren’t looking at them after they’ve been fed. Although having found a male and a female does not automatically mean success, it is a step on the way.
The ideal temperature is between 73°-83°F. Standard fluorescent bulbs are fine for the lighting. Piranhas also like some protective cover, and you should also produce the light of half of the aquarium darker than the other. Piranhas are hardy fish but it’s a good idea to maintain the water clear and clean. In their first Amazon River habitat, the rainy season is when most fish predominate. Frequent and larger water changes appear to have an immense influence on the success of breeding (as they simulate the rainy season) and are most helpful in getting the piranhas into breeding condition.
When your piranhas lose all their color and turn almost completely black, they are in breeding condition! Both of them may start to protect a specific place; chasing off other piranhas that come too near. When they begin picking up gravel in their mouths as if digging, it usually means they’ve already started the mating process. Be careful not to disturb your piranhas in this time! The female will release eggs into the pit, and then leave the nest (but might stay close by it). The male is usually responsible for guarding the nest and eggs. The number of eggs laid varies from 700-4000. The eggs hatch in 2-3 days.
If you are lucky enough to have reached this point, then it’s time to look after the fry. Be very, very careful when moving the fry, as the parents can be extremely protective and competitive. The fry will absorb their yolk sacs and you can start feeding them live baby brine shrimp as food.
One thing you should be conscious of is the legal troubles. Some states don’t allow the sell or possession of piranhas at all. Other states require that you get a permit to sell or own a piranha. Make certain to check to find out if any local restrictions apply before buying your piranhas.