This is one of the most attractive and popular of the tropical American characins. It mostly lives in a shoal in the middle water layers.
Females are usually a little larger than males.
The body is elongated and laterally compressed, and there is an adipose fin. The most striking feature, however, is the coloration. A broad, iridescent blue-green longitudinal band extends from the tip of the snout, through the eye, to the caudal peduncle. Below this there is a bright red band also extending to the base of the tail. Cardinal Tetras do best, and also look most attractive, when kept in subdued light in a tank with a dark substrate.