Each species of Tetra has its own specific distribution and range, though some species do overlay with the populations of others. Some live across broad areas, while others live in a single river system. Tetras live in a diversity of different regions. Tetras are endemic to South and Central America and Africa, with a considerable majority coming from the Amazon Basin, except for the blind cave tetra, which was discovered in a cave system in Mexico. Providing you take proper Care of your Tetra Fish, they can live for 5 to 10 years. Tetras can vary in size from 4 cm to 15 cm, although most Tetras available in the hobby are smaller. Species such as the Cardinal Tetra and Neon Tetra are among the most popular of all freshwater fish, adding a touch of social interaction and brilliance to the community aquarium. These fish also have a small, fleshy adipose fin found between the caudal and dorsal fins. Additionally, Tetras have a long anal fin extending from a posterior of the dorsal fin and ending on the ventral caudal peduncle. They commonly possess a tall dorsal fin and a homocercal caudal fin distinguished by a short connection to the fish's body. Tetras generally have compressed bodies and can be typically identified by their fins.

Consequently, they are prevalent in home aquariums. A majority of these fish are also brightly coloured and easy to take care of in captivity. Many of these fish have several bones that join the swim bladder and inner ear, enhancing these colourful fishes hearing. Even though this adipose fin is generally considered the distinguishing feature, some Tetras, such as the Emperor Tetra, lack this feature. This adipose fin factors the fourth unpaired fin on these fish. Characidae can be recognised from other fish by their small adipose fin between the dorsal fin and tail. There are currently over 100 tetra species divided up between the three families. Tetra is the well-known name of many small freshwater characiforms belonging to the biological family Characidae and its former subfamilies Lebiasinidae and Alestidae.

Wild bleeding heart tetra