The Cardinal Tetra (Paracheirodon axelrodi) is an extremely popular small tetra species. They stay small (approx. 2-inch total length) and are characterized by their incredibly colourful bodies. The top half of their bodies are an intense neon blue, while the bottom half is a vivid red. These fish look similar to Neon Tetra; the main difference is that the Cardinal Tetra's red stripe travels all the way across their bodies.
These fish do best in groups of 3 or more, and in temperatures in the mid-70's. A small group of 6 can be comfortably housed in a 10-gallon aquarium. These animals live for up to 4 years in captivity, but their lifespan is drastically reduced in hard water. Cardinal tetras do well in water with a neutral pH, but do best in water that is slightly acidic (pH of 4.6-6.2). These fish do best in soft water.
These animals are very easy to care for and can live easily with a large variety of fish. They will peacefully live with other small community fish.
(Image source "Aquarium Co-op")