The cardinal tetra has bright red ventral parts and an iridescent blue line that runs horizontally down the length of its body. The characteristic iridescence of this and related fishes, such as the neon tetra, is a structural color, caused by refraction of light within guanine crystals that develop within special cells called iridocytes in the subcutaneous layer. The exact shade of blue seen will depend on the viewing angle of the aquarist relative to the fish - if the aquarist changes viewpoint so as to look at the fish more from below, the colour will change hue, becoming more deeply sapphire blue and even indigo. Change the viewpoint to one above the fishes, however, and the color becomes more greenish. Cardinal tetras appear to grow larger in captivity than they do in the wild.They have a large stomach and small gut.
The cardinal tetra is an omnivorous species and will accept most foods. These fish have high vitamin requirements, so at least 75 percent of their food should be quality flake food. Cardinal tetras especially appreciate live and frozen foods, but if fed them exclusively they may reject prepared food later on. If only doing one to two feedings a day, offer what they can eat in about five minutes. However, it is better to feed these fish several times a day, offering only what they can eat in about three minutes. All foods should be in small pieces as cardinals have a small mouth. When conditioning breeders, live foods are important.
|pH||4.6 to 6.2|
|Hardness||Up to 4 dGH|
|Temperature||73 to 81 degrees F (23 to 27 degrees C)|