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 Blue Neon Goby (Stiphodon atropurpureus) is a small stream goby. Males show a vivid blue sheen. Found in short coastal streams in the Philippines, southern China, Taiwan, Japan and Malaysia. Grows to about 2 in (5 cm). Often sold under the wrong name,...
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 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 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 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 "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 "Gold Piranha" is a trade name for Serrasalmus maculatus, also called the golden mac. The name is sometimes applied to other Serrasalmus species. Widespread in the Amazon, Paraguay and Paraná basins of South America. Grows to about 8 in (21 cm) standard...
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 Peacock Gudgeon (Tateurndina ocellicauda) is a small, colorful sleeper (family Eleotridae), not a true goby. Native to lowland rainforest streams, ponds and rivers of eastern Papua New Guinea. Grows to about 3 in (7.5 cm) standard length. Feeding Accepts...
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 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 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 Red-bellied Piranha (Pygocentrus nattereri) is the most famous piranha, silver with a red belly. Found through much of the Amazon basin, plus the Essequibo and the Paraná–Paraguay system. Grows to about 14 in (35 cm) standard length. Illegal to own in...
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 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 Serpae Tetra (Hyphessobrycon eques), also called the jewel or callistus tetra, is a red tetra with a black shoulder spot. Found through much of the Amazon and the Río Paraguay. Grows to about 1.6 in (4 cm) standard length. Feeding Likely omnivorous....
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...