The Tambaqui (Colossoma macropomum) is a freshwater fish of the subfamily Serrasalminae, family Characidae. It is also known by the names Pacu, Black pacu, Black-finned pacu, Giant pacu, Cachama and Gamitana. It is the only species of the genus Colossoma.
It is similar in shape to the piranha and is sometimes confused with the carnivorous fish; the pacu is tall and laterally compressed with large eyes and a slightly arched back. Body color is basic black to gray with spots and blemishes in its mid body. All the fins are black and the pectoral fins are small. Around 10 percent of a tambaqui's weight is fat. The record recognized world by IGFA belongs to the Brazilian Jorge Masullo de Aguiar with 32,4 kg
This species is usually solitary. Adults stay in flooded forests during the first 5 months of flooding and consume fruits and grains. Young and juveniles live in black waters of flood plains until sexual maturity. The tambaqui feeds on zooplankton, insects, snails, and decaying plants.