tetra

thumb|right|250px|Black neon tetra, Hyphessobrycon herbertaxelrodi thumb|right|250px|Pristella tetra, Pristella maxillaris thumb|right|250px|Golden pristella tetra, a morph (zoology)|morph of [[Pristella maxillaris]] thumb|right|250px|Silvertip tetra, Hasemania nana

Tetra is the common name of many small freshwater characiform fishes. Tetras come from Africa, Central America, and South America, belonging to the biological families Characidae, Alestidae (the "African tetras"), Lepidarchidae, Lebiasinidae, Acestrorhynchidae, Stevardiidae, and Acestrorhamphidae. In the past, all of these families were placed in the Characidae. The Characidae and their allies are distinguished from other fish by the presence of a small adipose fin between the dorsal and caudal fins. Many of these, such as the neon tetra (Paracheirodon innesi), are brightly colored and easy to keep in captivity. Consequently, they are extremely popular for home aquaria.