Cardinal tetras are small, spindle-shaped fish. The cardinal tetra gets its name from its vibrant, red coloring and iridescent neon blue lateral stripe that runs from nose to tail. It has a blunt nose and translucent fins.
The color of the cardinal tetra’s lateral stripe changes depending on the light conditions. When resting at night, cardinal tetras lose their dazzling colors. A lack of coloration during daytime indicates stress or illness.
Cardinal tetras inhabit blackwater creeks and tributaries in the wild. These bodies of water are soft, acidic, and colored black from the tannins of decaying leaves.