Cardinal tetra fish have a horizontal bright, neon-like blue stripe and directly below it, a brilliant red stripe. These stripes run the entire length of their body, from the nose to the tail and take on an iridescent blue and green colouration as changes occur in the angle of light that strikes them. During the night and at times when no light hits the fish, they appear to be transparent and brown. The back and underbelly are whitish-silver. Males and females look the same, except females have a rounder belly. Cardinal tetras, as with other characids have an adipose fin (soft fleshy fin on the back located between dorsal and caudal fins).