Explore our growing database of freshwater fish species. Each profile includes detailed care requirements, compatibility data, and environmental needs to help you build the perfect aquarium.
Pangasianodon hypophthalmus
The Iridescent Shark is not a true shark, but a highly active, schooling catfish native to Southeast Asia. While frequently sold as tiny juveniles, they are notorious 'tank busters' that grow to massive sizes. They are extremely skittish and easily spooked, often injuring themselves by crashing into aquarium glass. They are best suited for heated indoor ponds or massive custom aquariums.
Rocio octofasciata
A robust, highly territorial Central American cichlid named after the aggressive 1920s boxer, William 'Jack' Dempsey. They exhibit beautiful iridescent blue, green, and gold spangling over a dark background. As aggressive diggers and plant destroyers, they require a tank with sturdy decor. They are best kept as a single wet pet or in a large tank with other similarly sized, robust Central American cichlids.
Parachromis managuensis
A massive, apex predator from Central America known for its striking jaguar-like pattern and extreme aggression. Jaguars are highly intelligent, wet-pet fish but require enormous aquariums and heavy filtration. They will consume any fish that fits in their mouth and aggressively rearrange their environment.
Oryzias latipes
A hardy, small, and colorful fish native to East Asia. Extremely popular in the outdoor pond hobby and nano aquariums. They are 'amphidromous' (tolerant of salinity changes) and can survive a wide range of temperatures, making them excellent tub/pond fish. They are surface dwellers that look best when viewed from above (top-down).
Melanotaenia japenensis
The Japen (or Yapen) Rainbowfish is a rare and striking schooling species endemic to Yapen Island in Papua, Indonesia. Like most rainbowfish, they are active swimmers that display their best colors in established aquariums with high water quality and plenty of horizontal swimming space. They are sexually dimorphic and thrive in slightly alkaline, moderately hard water.
Corydoras trilineatus
Often sold in the aquarium trade as the 'Julii Cory', the False Julii (Corydoras trilineatus) is a peaceful, highly social bottom-dweller. It features a distinct reticulated (maze-like) pattern on its head and a prominent horizontal stripe down its body. As an obligate schooling fish, it must be kept in groups to thrive and feel secure. A soft sand substrate is absolutely critical to prevent the erosion of their sensitive foraging barbels.
Satanoperca jurupari
The Jurupari Eartheater is a remarkably peaceful South American cichlid famous for its continuous substrate-sifting behavior. They require a fine sand substrate to thrive and prevent damage to their delicate gills. Unlike highly aggressive cichlids, they are gentle giants that prefer the company of their own kind in a large, uncrowded community of similar-sized peaceful fish.
Melanotaenia kamaka
Endemic to the karst Lake Kamakawai in West Papua, this is a spectacular and distinctively deep-bodied rainbowfish. As they mature, males develop a robust chest and an intense silvery-blue to purplish sheen. Like all rainbowfish, they are highly active, schooling fish that require spacious tanks with plenty of horizontal swimming room and alkaline, hard water parameters.
Maylandia lombardoi
The Kenyi Cichlid is a stunning but notoriously aggressive Mbuna from Lake Malawi. They exhibit extreme sexual dimorphism: females and juveniles are pale blue with dark vertical bars, while mature males undergo a complete transformation to a vibrant golden-yellow. Due to their extreme territoriality, they must be kept in large, overstocked, rock-heavy tanks to disperse aggression, typically in a harem (one male to multiple females).
Cleithracara maronii
A remarkably peaceful and shy South American cichlid, named for the distinctive keyhole-shaped black marking on its flank. Unlike many of its cousins, it rarely digs or destroys plants and makes an excellent resident for a peaceful community tank. When stressed or frightened, it can rapidly mottle its colors to blend in with its surroundings.
Helostoma temminckii
A large, heavily-built labyrinth fish famous for its 'kissing' behavior. This kissing is actually a form of territorial sparring, mostly between males asserting dominance. They are specialized filter-feeders and grazers that use their raspy lips to scrape algae. Because they grow surprisingly large (up to 10-12 inches) and are prone to eating live plants, they require spacious aquariums and specific diets.
Kiunga ballochi
A tiny, critically rare micro-predator native to a very restricted area in the Upper Fly River system of Papua New Guinea. Characterized by a transparent 'glass' body with striking yellow and black fin margins. They are peaceful shoaling fish that require highly stable water conditions and a planted aquarium. Listed as Endangered on the IUCN Red List, they are a true rarity in the aquarium trade.
Stigmatogobius sadanundio
A distinct, high-bodied goby found in estuaries across South Asia. Unlike most bottom-dwelling gobies, the Knight Goby frequently hovers in the water column. While often sold as freshwater fish, they thrive best in slightly brackish water (SG 1.003-1.005) or very hard, alkaline freshwater. They are territorial and notorious fin-nippers, making them poor tankmates for Guppies or Bettas.
Cyprinus rubrofuscus
Koi are large, ornamental varieties of the Amur carp. They are massive, long-lived pond fish that produce an extreme amount of waste. Highly social and intelligent, they can learn to recognize their owners. Due to their immense adult size, they are entirely unsuitable for indoor aquariums and require a very large pond with heavy filtration for their adult life.
Pelvicachromis pulcher
A vibrant and highly popular dwarf cichlid native to the slow-moving rivers of West Africa. Unlike Rift Lake African cichlids, they prefer soft, slightly acidic water and densely planted tanks. They are generally peaceful in a community tank but become fiercely territorial and aggressive when breeding, often digging pits in the substrate and claiming the bottom zone. They are cave spawners and require hiding spots like driftwood or coconut shells.
Pangio kuhlii
A remarkably peaceful, eel-like bottom dweller native to the slow-moving forest streams of Southeast Asia. Famous for its orange and dark brown banding, the Kuhli Loach is an excellent scavenger. They are notoriously shy and nocturnal, requiring dense planting, leaf litter, and most importantly, a soft sand substrate to burrow in without damaging their delicate barbels. They must be kept in groups to feel secure and prevent severe stress.
Scleromystax lacerdai
A rare and beautiful bottom-dweller endemic to coastal Brazilian streams (Bahia). Unlike typical tropical Corydoras, it is a temperate/sub-tropical species that requires cooler water (20-25°C). They are highly sexually dimorphic and must be kept on a soft sand substrate to protect their delicate sensory barbels.
Melanotaenia eachamensis
The Lake Eacham Rainbowfish is a rare, highly active shoaling fish from Australia. It is famous in conservation circles for having been extirpated in its namesake crater lake, though it survives in surrounding watersheds and the aquarium hobby. They are peaceful but voracious surface feeders that require pristine water, moderate flow, and ample horizontal swimming space to thrive.
Pelangia mbutaensis
A very rare and Critically Endangered rainbowfish endemic to the swampy Lake Mbuta basin in West Papua, Indonesia. It is the sole member of the genus Pelangia. Characterized by a yellowish-tan body grading to silvery-white, they are peaceful, active schooling fish. They are virtually unseen in the standard aquarium trade.
Melanotaenia herbertaxelrodi
A striking, highly active schooling fish endemic to Lake Tebera in Papua New Guinea. They feature bright yellow to greenish-blue bodies with a distinct dark lateral stripe. As vigorous swimmers, they require long aquariums and do best in mixed-sex shoals, which encourages males to display their best colors. Due to their highland origin, they prefer slightly cooler, well-oxygenated, and alkaline water.
Glossolepis wanamensis
A critically endangered species (IUCN Red List) endemic to Lake Wanam in Papua New Guinea. Known for the extreme deep-bodied shape and metallic green-bronze colors that mature males develop. They are fast, active schooling fish that require hard, alkaline water and plenty of swimming space. Excellent for large planted aquariums.
Micropterus salmoides
An iconic North American game fish occasionally kept by 'monster fish' enthusiasts. They are highly intelligent, robust, and voracious apex predators with cavernous mouths capable of swallowing surprisingly large prey. Because of their massive adult size, rapid growth, and heavy bioload, they are strictly suited for massive custom aquariums or indoor/outdoor ponds.
Micropanchax macrophthalmus
A peaceful, nano-sized schooling killifish native to West Africa. They are renowned for the brilliant, iridescent blue or green reflective spot on the upper part of their eye. Unlike seasonal killifish, they are relatively long-lived (2-4 years). They require well-established, densely planted aquariums and must be kept in groups to feel secure and display their best colors.
Heterandria formosa
Despite its common name, the Least Killifish is actually one of the smallest livebearing fish in the world, belonging to the Poeciliidae family, not the killifish family. Native to the southeastern United States, they are incredibly peaceful and perfect for nano tanks. Unlike most livebearers, they exhibit 'superfoetation', meaning females drop 1-2 fry every few days rather than a large single brood.
