Here are some of the most popular freshwater fish species that are commonly kept in aquariums, each with unique characteristics and care requirements.
A common rule of thumb for how many freshwater fish you can keep in an aquarium is to allow about 1 inch of fish per gallon of water; however, this can vary depending on the specific fish species, their adult size, activity level, and bioload, with heavily planted or densely stocked tanks often needing more filtration and swimming room.
Overview The Betta (Betta splendens), or Siamese fighting fish, is one of the best-known aquarium fish. Native to central Thailand, where it lives in rice paddies, swamps, ditches and slow streams. Wild fish reach about 2.8 in (7 cm) standard length. Long-finned...
Overview The Black Molly is a black, captive-bred form of the common molly (Poecilia sphenops). Wild mollies range from Mexico south to Colombia and Venezuela. Grows to about 3.1 in (8 cm). Many black mollies in stores are hybrids with other molly species. Feeding...
Overview The Clown Loach (Chromobotia macracanthus) is a bright orange loach with black bands. It is very popular, but often bought without knowing how big it gets. Native to rivers of Borneo and Sumatra in Indonesia. Can reach about 16 in (40 cm), though it grows...
Overview The Dwarf Gourami (Trichogaster lalius) is a colorful labyrinth fish. Males have red and blue bars. Native to Pakistan, northern India and Bangladesh, in slow, heavily planted ponds, swamps, ditches and canals. Grows to about 3.5 in (8.8 cm) standard length....
Overview The Green Swordtail (Xiphophorus hellerii) is the wild-type form of the familiar swordtail. Males grow a long "sword" on the lower tail fin. Native to southeastern Mexico, Guatemala, Belize and Honduras. Grows to about 6 in (14 cm) standard length. The sword...
Overview The Endler's Guppy (Poecilia wingei) is a tiny, brilliantly colored livebearer related to the common guppy. Native to lagoons in northeastern Venezuela, such as Laguna de Patos. Males grow to about 1 in (2.5 cm) standard length. Females are larger. Hybridizes...
Overview "Dwarf Snakehead" usually refers to Channa gachua. The name is also used for other small snakeheads such as C. bleheri and C. andrao. C. gachua has a huge range from Iran to Taiwan and Bali. It is probably a complex of several similar species. Grows to about...
Overview The Honey Gourami (Trichogaster chuna) is a small, peaceful gourami. Breeding males turn honey-orange with a dark throat. Native to the Ganges and Brahmaputra basins of northern India and Bangladesh. Grows to about 2.2 in (5.5 cm) standard length. A good...
Overview The Platinum Guppy is a metallic white strain of the common guppy (Poecilia reticulata). Wild guppies come from northeastern South America and the southern Caribbean, including Venezuela, the Guianas and Trinidad. Females grow to about 2.4 in (6 cm). Males...
Overview The Pearl Gourami (Trichopodus leerii) is a graceful gourami covered in pearly white spots. Breeding males develop a deep orange throat. Native to lowland swamps of Thailand, Malaysia, Borneo and Sumatra. Grows to about 5 in (12 cm) standard length. Hardy,...
Overview The Opaline Gourami is a captive-bred color form of the three spot gourami (Trichopodus trichopterus). It has a marbled blue pattern. Wild three spot gouramis live in slow, weedy lowland waters of the Mekong basin and Southeast Asia. Grows to about 6 in (15...
Overview The Kuhli Loach is a slender, eel-like loach with orange and dark bands. It is sold as Pangio kuhlii. Most trade fish are actually Pangio semicincta from Peninsular Malaysia, Sumatra and Borneo. True P. kuhlii is from Java and is rarely exported. Grows to...
Overview The Red Wagtail Platy is a red strain of the southern platyfish (Xiphophorus maculatus) with black fins and tail. Wild platies live in streams and rivers on the Atlantic coastal plain of Mexico, Guatemala, Belize and Nicaragua. Grows to about 2 in (5 cm)...
Overview The Zebra Loach (Botia striata) is a small botiid with fine yellow and dark stripes. Native to the Western Ghats region of southern India, described from the Tunga River. Grows to about 3.5 in (9 cm) standard length. Probably the best Botia for general...
Overview The Yoyo Loach is usually sold as Botia almorhae. Its pale body has dark markings that can look like the letters "YOYO." Many trade fish may be B. lohachata or related species. The true appearance of B. almorhae is unclear. Native to northern India and Nepal....
Overview The Sailfin Molly (Poecilia latipinna) is a large molly. Males have a tall, sail-like dorsal fin. Native to the southern United States and Mexico, from the Carolinas to Veracruz, often in coastal and brackish waters. Grows to about 5 in (12.5 cm) standard...
Overview The Yucatan Sailfin Molly (Poecilia velifera), also called the giant sailfin molly, is the largest of the sailfin mollies. Mature males carry a huge, sail-shaped dorsal fin. Wild fish come only from southeastern Mexico, in the Yucatán and Quintana Roo region...