Learn About Cardinal Tetra - as part of the expert series by GeoBeats. Not just United States but in entire world the most popular which is the Cardinal Tetra because of its bright red and blue coloration. The fact that it will live in almost any aquarium setting as far as community tanks. Does well as a big group or in smaller numbers. Does well with plants and its not aggressive so I presume that is probably why it is such a popular fish. It is endemic to several areas, comes from Brazil as well as Columbia. There does appear to be a little bit of variation between the two different forms, one has a little more red, the other has a little more blue, but most forms are very similar. It is an interesting fact too, that this fish is the reason there is a tropical fish business in Brazil because it is by far the leading export of fish from Brazil. If it was not for this fish we probably would not see a lot of the other interesting fish we do from Brazil, because this fish makes the shipments possible.