Care Level

The Rummynose (Firehead Tetra), native to South America, is easy to keep in a small freshwater aquarium. The Four-eyed Butterflyfish, occurring naturally in the South Atlantic, Gulf of Mexico and Caribbean region, requires more attention to get this species to eat the right fish food. Some species are sensitive to changes in water quality, and aquarium filters must be cleaned often along with regular water testing.

Adult Size

Many small freshwater species including Neon Tetras, Swordtails, Tiger Barbs, and Danios do well in a 10- to 20-gallon aquarium. Larger, more territorial fish (such as African Cichlids) need more space. Popular Clownfish species are about 3-4 inches as adults and can be kept in a smaller marine aquarium. Adult Yellow Tangs reach 6 inches in length and are better suited for a medium-sized saltwater tank.

Most saltwater fish need a minimum of 29-gallon tanks. Dartfish, Gobies and Damselfish (Indo-Pacific species) can be kept in smaller marine aquaria. The Bluehead Wrasse from Central and South America needs an intermediate sized tank (75 gallons), while the Royal Blue Tang needs a tank twice that large. The Gray Angelfish (south Atlantic, Gulf of Mexico, Caribbean) can reach 20 inches as an adult, requiring an aquarium as large as 200 gallons.

Temperament

By nature, some fish are peaceful while others are more aggressive and territorial. Marine Flame Angels are not large as adults (6 inches) but are somewhat territorial. Freshwater Angelfish, found naturally in the Amazon River basin, are also semi-territorial and should be kept in a larger freshwater aquarium. Among marine species, Blennies are smaller peaceful species where Blue Jaw Triggerfish are territorial. Although popular for freshwater tanks, many African Cichlids are aggressive species that should not be kept in smaller aquaria.

A species’ behavior helps in choosing compatible species. The Tobacco Basslet, actually a member of the sea bass family, is a territorial species that will tolerate similar size peaceful or semi-territorial fish. Among freshwater tropical fish, Bettas (Fighting Fish) should not be kept with other males of the same species. Cherry Barbs, native to southeast Asia, are timid fish that can be kept with other peaceful species.

Diet

Popular aquarium species may be carnivores, herbivores or omnivores. Some consume pellets while others prefer flakes of dried food from algae, plankton, marine shrimp and other invertebrates. Take note of whether your species feeds at the top, mid-tank or on the bottom. If you plan on having fish and coral in your tank, check to see if the fish are reef safe: some species, like Spanish Hogfish, will damage corals.