Piranhas are carnivorous fish that feed on dead or dying animals and some species also eat fruits and nuts during high water seasons. While they have a reputation for being ferocious, piranhas are not actually vicious and can be kept with other fish if given a lot of space and extreme care and attention. Piranhas have reddish bellies, razor sharp teeth that can rip flesh, and grow up to 33 cm long and 3.5 kg as adults.