Characins or tetras are a fairly hardy fish. They do better in schools, rather than alone in the home aquarium. Tetras are not recommended to cycle a new aquarium, ammonia levels usually get above their limits, and will kill them. This is an immense family of fishes of almost unbelievable diversity. Conservative estimates of the number of species of cichlids range from 1300 to many, many more.
Cichlids come in a surprising diversity of shapes, sizes and colours.
They share a few common characteristics, including life in freshwater and advanced forms of parental care of their young. These characteristics do not define the cichlids, because many other fishes also have these characteristics and yet are not cichlids, but they do explain part of the immense popularity of these fishes for aquarists. The Cyprinids consist of Danios, Barbs, Rasboras, Sharks and a few others. They are generally toothless fish with sensory fingers, or barbels on their mouths. The toothed variety have teeth in their throats.