Characiformes is an order of ray-finned fish, comprising the characins and their allies. Grouped in 18 recognized families, more than 2000 different species are described, including the well-known piranha and tetras. Characins are most diverse in the Neotropics, where they are found in lakes and rivers throughout most of South and Central America. At least 209 species of characins are found in Africa, including the distichodontids, citharinids, alestids, and hepsetids. The rest of the characins originate in the Americas.

A few characins become quite large, and are important as food or game. Most, however, are small shoaling fish (or forage fish). Many species commonly called tetras are popular in aquaria because of their bright colors, general hardiness, and tolerance towards other fish in community tanks.

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