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 One of the most popular and recognizable aquarium fish. Lives in acidic forest streams, often stained with tannins (blackwater), with leaf litter and roots. Has a bright blue lateral stripe. The red pigment does not extend forward past the pectoral-fin base....
Overview The Black Phantom Tetra (Hyphessobrycon megalopterus) is a peaceful, smoky-gray tetra with a black shoulder spot and large fins. Native to the upper Rio Madeira basin in Bolivia and western Brazil, and the Rio Paraguay basin. Grows to about 1.4 in (3.6 cm)...
Overview The Black Skirt Tetra (Gymnocorymbus ternetzi), also known as the Black Widow Tetra, is a hardy, deep-bodied tetra with black vertical bars and a dark rear half. Native to slow creeks and streams with overhanging plants in the Paraguay and Guaporé basins of...
Overview The Bloodfin Tetra (Aphyocharax anisitsi) is a silvery tetra with bright red fins. Native to the Paraná River basin in Brazil, Paraguay and Argentina. Grows to about 2.2 in (5.5 cm) standard length. A hardy beginner fish that adapts to a wide range of...
Overview The Bolivian Ram (Mikrogeophagus altispinosus) is a peaceful dwarf cichlid. It is also sold as the Bolivian butterfly cichlid. Native to the upper Rio Madeira basin in Bolivia and Brazil. Grows to about 3.1 in (8 cm) standard length. Usually a better choice...
Overview The Cardinal Tetra (Paracheirodon axelrodi) has a neon-blue stripe above a red lower body that runs the full length of the body. Native to forest streams in the Rio Negro and upper Orinoco basins of Brazil, Colombia and Venezuela. Grows to about 1.4 in (3.5...
Overview The Discus (Symphysodon aequifasciatus and related Symphysodon species) is a disc-shaped Amazon cichlid prized for its color. Wild fish live in slow tributaries and forest pools along the Rio Solimões and Amazon. Grows to about 6 in (15 cm) long and nearly as...
Overview The Colombian Tetra (Hyphessobrycon columbianus) is a robust tetra with a blue-silver body and red fins. It is also sold as the blue-red or Colombian red fin tetra. Known only from the Río Acandí area in northern Colombia, near the Panama border. Grows to...
Overview The Harlequin Rasbora (Trigonostigma heteromorpha) is a classic schooling fish with a copper body and a black triangle on the rear half. Native to southern Thailand, Peninsular Malaysia, Singapore, Sumatra and Borneo. Grows to about 1.8 in (4.5 cm) standard...
Overview The Glowlight Rasbora (Trigonopoma pauciperforatum), also sold as the redline rasbora, is a slim rasbora with a glowing orange-to-gold stripe. Native to Peninsular Malaysia, Singapore, Sumatra and Borneo. Grows to about 2.4 in (6 cm) standard length. Lives in...
Overview The Glowlight Tetra (Hemigrammus erythrozonus) is a small, peaceful tetra with a glowing orange-red stripe. Known only from the Rio Essequibo in Guyana. Grows to about 1.6 in (4 cm) standard length. All fish sold are commercially farmed. An albino form is...
Overview The German Blue Ram (Mikrogeophagus ramirezi), also called Ramirez's dwarf cichlid or butterfly cichlid, is a small, jewel-like dwarf cichlid. Native to the llanos savanna wetlands of the Orinoco basin in Venezuela and Colombia. Grows to about 1.6 in (4 cm)...
Overview The Espe's Rasbora (Trigonostigma espei), also called the false harlequin or lambchop rasbora, is a small copper-orange rasbora with a black wedge mark. Native to forest streams in southwestern and southeastern Thailand and nearby Cambodia. Grows to about 1.2...
Overview "Pencilfish" covers several slim Nannostomus species. This profile follows the most common one, the golden pencilfish (Nannostomus beckfordi). N. beckfordi is found in Guyana, Suriname, French Guiana and parts of the Amazon basin. Grows to about 2.6 in (6.5...
Overview The Mexican Tetra (Astyanax mexicanus) is best known in its blind cave form, the blind cave tetra. The species ranges from Texas and New Mexico through Mexico to Guatemala. The eyeless form lives only in Mexican caves. Grows to about 3.7 in (9.5 cm) standard...
Overview The X-Ray Tetra (Pristella maxillaris) is a semi-transparent tetra with black, yellow and white fin markings. Native to coastal waters of Venezuela, the Guianas and northern Brazil. Grows to about 1.8 in (4.5 cm) standard length. Commercially bred and one of...
Overview The Scarlet Badis (Dario dario) is one of the smallest percoid fish. Males are bright red with blue bars. Found in tributaries of the Brahmaputra in West Bengal and Assam, India. Grows to about 0.8 in (2 cm) standard length. A popular nano fish. Feeding A...