Though not usually called community tanks, most marine aquaria fit into this category too, using fish from places as diverse as the Caribbean, Red Sea, and western Pacific Ocean.
Other aquarists prefer communities that represent particular locations, and combine fishes from a certain place with appropriate decorative materials including the right kinds of rocks and plants. The most popular of these geographically correct community tanks are those based around cichlids from the East African Rift Valley lakes of Lake Tanganyika and Lake Malawi.
Good community fish
For freshwater community tanks, there are large numbers of species that work well. Most of the livebearers, barbs, tetras, rasboras, danios, and rainbowfish are peaceful, though a few species are fin nippers, most notably tiger barbs and serpae tetras. Angelfish, gouramis, and dwarf catfish (Corydoras) can also work well, though angelfish at least are predatory and will eat very small fish such as neon tetras.
Notoriously bad community fish include the red-tailed black shark, the sucking loach Gyrinocheilus aymonieri, and many types of cichlid and catfish. These fish are often aggressive and/or predatory, so are best kept in species tanks or in carefully constructed communities with other robust species.
Most freshwater aquarium fish do well in water that is soft to moderately hard, and has a pH between 6 and 8; the notable exceptions are the Poeciliidae such as guppies and mollies, which should generally only be kept in hard, alkaline water.
Brackish water aquaria are another special case and need their own community tanks. While a few freshwater and marine fish can adapt to brackish water, most cannot .