Red-bellied piranhas are infamous as bloodthirsty, viscous carnivorous fish. However, although they are aggressive and dangerous towards other fish, red-bellied piranhas are usually only dangerous towards humans when they are starving. In fact, these fascinating creatures can make interesting and unusual home aquarium inhabitants. Red-bellied piranhas also breed readily in an aquarium, when the right conditions are provided. These fish guard and care for their eggs and young. It can be captivating to watch this species as it breeds and raises the young fish.
Observe the red-bellied piranhas. These fish reach sexual maturity when they are between five and six inches long. It's at this age that you'll be able to determine which fish are female, and which are male. It's also when you'll be able to begin breeding them. Female piranhas will become much fatter than the males, and will develop a purple hue. Male red-bellied piranhas will develop a dark blue or black colouration.
Set up a freshwater breeding aquarium for the piranhas. Because of the enormous number of young fish likely to develop, you'll need an aquarium 50 gallons or larger in order to breed one pair of fish.
Place several leafy plants in the aquarium. These plants mimic the natural habitat of the fish, provide hiding places so the fish feel safer, and are also where the piranhas will usually lay their eggs.
Install a thermometer in the breeding aquarium. Maintain a water temperature between 23.9 and 26.7 degrees Celsius. If the water is not warm enough, use an aquarium water heater.
Place the female piranha in the aquarium where you'll be breeding the fish. The female should be placed in the aquarium by herself so that she has time to explore and become comfortable in the new environment. Let the female red-bellied piranha explore for between three and seven days.
Place the male piranha in the breeding aquarium with the female.
Feed the red-bellied piranhas frequently. Feeder goldfish are well suited to this task, as they can be placed in the breeding aquarium with the piranhas, and the carnivorous fish can eat them whenever they feel the need. Underfeeding can result in the male and female red-bellied piranhas attacking each other.
Wait for the red-bellied piranhas to breed. This should happen almost immediately. Thousands of tiny orange eggs will be laid at the bottom of the aquarium. These eggs hatch within about 56 hours. The parent piranhas will guard the eggs and the young.