More than 1400 species are known. Characins can be recognized by the presence of a short, stublike adipose fin located between the tail and the dorsal fin. Many species are small and brilliantly colored, such as the neon tetras popular among aquarists. Some species are strictly herbivorous, while others feed on fishes. Most characins scatter their eggs among aquatic plants, where the young are protected from predators.
Some species migrate during the spawning season to habitats with dense aquatic vegetation.
Piranhas and pakus are among the well-known larger species of characins. The common red-bellied piranha may engage in a feeding frenzy when it encounters a bleeding animal. However, most piranha species are docile vegetarians, feeding on fruits, seeds, and leaves that have fallen into the water from overhanging trees. The neon tetra is classified as Hyphessobrycon innesi, the African tigerfish as Hydrocynus goliath, the Bolivian pygmy blue characin as Xenurobrycon polyancistrus, the red-bellied piranha as Pygocentrus natereri, and the tambaqui as Colossoma macropomum.