They ordinarily possess a homocercal caudal fin (a twin-lobed, or forked, tail fin whose upper and lower lobes are of equal size) and a tall dorsal fin characterized by a short connection to the fish's body. Tetras generally have compressed (sometimes deep), fusiform bodies and are typically identifiable by their fins. For example, payara ( Hydrolycus scomberoides) is occasionally known as the ' sabretooth tetra' or 'vampire tetra'. Even vastly different fish may be called tetras. It is short for Tetragonopterus, a genus name formerly applied to many of these fish, which is Greek for 'square-finned' (literally, four-sided-wing).īecause of the popularity of tetras in the fishkeeping hobby, many unrelated fish are commonly known as tetras, including species from different families. Tetra is no longer a taxonomic, phylogenetic term. Consequently, they are extremely popular for home aquaria. Many of these, such as the neon tetra ( Paracheirodon innesi), are brightly colored and easy to keep in captivity.

The Characidae are distinguished from other fish by the presence of a small adipose fin between the dorsal and caudal fins. Tetras come from Africa, Central America, and South America, belonging to the biological family Characidae and to its former subfamilies Alestidae (the 'African tetras') and Lebiasinidae. Tetra is the common name of many small freshwater characiform fishes.

Gold tetra