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 Bristlenose Pleco (Ancistrus cf. cirrhosus) is the familiar bristlenose catfish sold in most stores. Males grow fleshy bristles on the snout. Grows to about 5 in (12.5 cm) standard length, much smaller than the common pleco. Mass-bred commercially. Its...
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 "Common Pleco" is a trade name for several large suckermouth catfish, most often the Amazon sailfin catfish (Pterygoplichthys pardalis). Store fish may be a related species or Hypostomus plecostomus. P. pardalis is native to the Amazon basin in Brazil and...
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 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 "Otocinclus" or "oto" covers several small algae-eating catfish. The one sold most often is probably Otocinclus macrospilus. Shipments are often mixed species. O. macrospilus comes from the upper Amazon in Peru, and possibly Colombia and Ecuador. Grows to...
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 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 Sailfin Pleco (Pterygoplichthys gibbiceps) is a large suckermouth catfish with a tall dorsal fin and a leopard-like pattern. Native to the Amazon and Orinoco basins in Brazil, Ecuador, Peru and Venezuela. Can reach around 18–20 in (45–50 cm). Feeding An...
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...