These are tall fish which give the appearance of a Red-bellied Piranha (Pygocentrus nattereri but they tend to be somewhat plumper despite the fact that the two are often confused. The most significant morphological difference between the two is the the level of protrusion of the jaw (much smaller in pacus than in piranhas). This helps to illustrate the largely vegetarian nature of the pacu and the largely carnivorous nature of the piranha. They are either grey or silvery fish with red bellies and the pacu has red lower body fins as well. The tambaqui also grows to a size which Pygo. nattereri can never hope to achieve. The genus to which the tambaqui formerly belonged, Colossoma was, at the time, the only genus of fish in which true molars are present. All genera which sprang from Colossoma are now among that still-somewhat-small assortment. Though they aren't to be feared as much as piranhas, tambaquis have formidable teeth which will be used on careless keepers that anger or scare them. The name Serrasalmidae means "Salmons with a Saw" (David Schleser, "Piranhas: A Complete Owners' Manual"), and this accurately describes the dentition of the Pacus.

Breeding: Egglayer - not bred in aquariums Minimum recommended tank size: 300 gallons with at least additional 200 gallons for every other Pacu.

A fascinating tropical fish species. We have learned that keeping Pacu as pets is a great experience. We found that Pacu add a lot of excitement to the home and caring for Pacu can be a challenge unless their owners are prepared with the right aquarium, food, filters, tank mates, etc. From instant household conversation topics to relaxing forms of motion-filled art Tropical Red Bellied Pacu grasp the attention and spawn the atmosphere of tranquility. Pacus do best when kept in shoals when they are young but have been found to live solitarily in the wild as they age. They are known to dispatch glass-encased heaters with some regularity and should thus be either shielded from them or kept warm via titanium heaters.

The basins of the Amazon and Orinoco Rivers. This is the most common Pacu and, as such, is known simply as "Pacu" in some regions of North America. The Houston Zoo's webpage provided quite a bit of information on this fish.