There are thousands of types of aquarium fish available. The aquarium fish are mainly divided into two major groups – freshwater aquarium fish and marine water aquarium fish. The setup, requirements, and maintenance of a freshwater aquarium differ from marine water fish tank; therefore, you cannot keep these fish together! Within these groups, many other types are available. Generally, the marine water fish are more brightly coloured than freshwater aquarium fish.

Some of the aquarium fish are diurnal in nature; however, some are nocturnal. Normally, during day time, the nocturnal fish are dormant and they hide inside the aquarium ornaments or in between aquarium plants, they will come out only during night time. Above all, the main classification of the aquarium fish is based on the social behaviour and aggressiveness of the fish. Based on these features, the aquarium fish are mainly divided into three major types; they are community fish, semi-aggressive fish, and aggressive fish.

The community fish are generally very calm and they do well in sharing the fish tank where they live. These are the best choice for the beginners. Most of the community fish are really hardy and they are easier to maintain. Some of the popular community fish are barbs, guppy, molly, neon tetra, platy, and widow tetra.

The semi-aggressive fish can do well in community aquariums; however, they may cause annoyance to smaller and less boisterous fish. It is suggested to keep only one of their types. Some of the popular semi-aggressive fish are angelfish, aurora cichlid, blue gourami, rainbow shark, red-tailed shark, and tiger barbs.
Aggressive fish are generally larger and territorial fish. Normally, these fish feed only on live foods. Usually, these fish are kept in a separate fish tank along with the fish of same kind. Some of the well-known aggressive fish are auratus cichlid, cobalt zebra, green terrors, Indian algae-eater, oscar, piranha, tiger oscars, and zebra cichlid.