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.
Betta macrostoma
Known as the 'Brunei Beauty', Betta macrostoma is a large, highly sought-after wild mouthbrooding Betta. They possess a massive mouth and are voracious predators. Native to highly acidic, soft blackwater streams in Borneo, they require cool, pristine water to thrive. They are extremely prone to jumping and require a tight-fitting lid.
Betta smaragdina
A beautiful wild-type Betta species native to the Khorat Plateau of Thailand, known for its striking iridescent emerald-green scales. Unlike the domestic Betta splendens, they are slightly more peaceful and closely resemble their natural wild form. They are excellent jumpers and require tight-fitting lids.
Cichlasoma bimaculatum
A hardy, adaptable, and robust South American cichlid. They are relatively peaceful compared to larger cichlids but become highly territorial when breeding. Known for their oval-shaped body, greyish-green coloration, and a distinct black mid-lateral spot. They naturally sift through the substrate and require sandy bottoms.
Vieja maculicauda
A large, powerful, and strikingly colored Central American cichlid known for the distinctive vertical black band across its midsection and vivid red flushing on its throat and tail. They are highly territorial, aggressive, and notorious for re-arranging the aquarium. They are primarily herbivorous in the wild but will eat almost anything, including smaller fish. They cannot be kept in planted tanks.
Ameiurus melas
The Black Bullhead is a hardy, heavy-bodied North American catfish. Highly adaptable and extremely predatory, it is known for eating anything that can fit into its exceptionally large mouth. Due to its massive adult size, rapid growth, and extreme bioload, it requires an extremely large aquarium or an outdoor pond. They are primarily nocturnal bottom-dwellers.
Corydoras schultzei
The Black Cory is a striking, deeply melanistic morph of Corydoras schultzei (often confused with C. aeneus). These peaceful, armored bottom-dwellers are highly social and must be kept in large groups to thrive. A soft sand substrate is absolutely critical to prevent damage to their sensitive foraging barbels.
Paratilapia polleni
A striking, highly intelligent cichlid native to the island of Madagascar. Commonly known as the Starry Night Cichlid due to its velvety jet-black body covered in brilliant iridescent white, blue, or gold spots. They possess a large mouth and are piscivorous (fish-eating), making them a threat to smaller tank mates. They are robust, aggressively territorial, and best kept as solitary showpiece fish or in heavily managed, large cichlid communities.
Corydoras leucomelas
A peaceful schooling catfish native to the Amazon basin, easily identified by its black dorsal fin and a dark mask-like band across its eyes. Like all Corydoras, they are bottom-dwellers that use sensitive barbels to forage. They possess a modified intestine allowing them to gulp atmospheric air, so occasional darts to the surface are normal. They are highly social and require a soft sandy substrate to prevent barbel erosion.
Apteronotus albifrons
A fascinating nocturnal predator native to the Amazon basin. It lacks a dorsal fin and moves via a continuous undulating ventral fin, allowing it to swim backwards as easily as forwards. It generates a weak electrical field to navigate and hunt in the dark. Scaleless and highly sensitive to medications, it requires smooth hiding places (like PVC pipes or smooth driftwood). Will consume any fish small enough to fit in its surprisingly large mouth.
Pangio oblonga
A peaceful, eel-like bottom dweller known for its solid dark brown to black coloration. Like other Kuhli loaches, they are strictly nocturnal scavengers that require a fine sand substrate to burrow and sift through without damaging their delicate barbels. They are highly social and must be kept in groups to feel secure and exhibit natural behaviors.
Megalechis thoracata
The Black Marble Hoplo is a hardy, active armored catfish from South America. Known for its generally peaceful nature and adaptability, it's an excellent scavenger. Uniquely among catfish, they can breathe atmospheric air from the surface and males are bubble-nesters.
Hyphessobrycon herbertaxelrodi
A peaceful, active schooling fish native to the Paraguay basin. Known for its striking contrast of a dark black lateral stripe underneath a glowing iridescent white/green-gold stripe. Excellent for community aquariums, particularly in planted setups or blackwater biotope tanks with subdued lighting.
Lamprologus speciosus
The Black Ocellatus is a highly entertaining and fiercely territorial shell-dwelling cichlid from Lake Tanganyika. Despite their tiny size, they have a massive personality and will vigorously defend their chosen snail shell from fish much larger than themselves. They require a sandy substrate to bury their shells and hard, alkaline water to thrive.
Colossoma macropomum
The Black Pacu (Tambaqui) is a massive, incredibly fast-growing Amazonian fish. Closely related to Piranhas, they possess crushing, human-like teeth evolved for cracking nuts and seeds. Due to their enormous adult size (often exceeding 3 feet and 60 lbs) and extreme bioload, they are completely unsuitable for standard home aquariums and require colossal custom tanks or heated indoor ponds.
Hyphessobrycon megalopterus
A peaceful, deep-bodied schooling tetra native to the Guaporé and Paraguay river basins. They are named for the distinct 'phantom' black patch behind their gills. They thrive in heavily planted tanks with subdued lighting (often achieved via floating plants or blackwater conditions). Males engage in spectacular but harmless 'mock battles' where they flare their fins at each other.
Pethia nigrofasciata
An active, schooling cyprinid endemic to the shaded forest streams of Sri Lanka. They are peaceful but highly energetic, making excellent community fish for cooler tropical setups. Unlike the notorious Tiger Barb, Black Rubies are generally peaceful and rarely nip fins, provided they are kept in a proper shoal of at least 6. Their deep colors emerge best in heavily planted, slightly dim environments.
Gymnocorymbus ternetzi
A very hardy, deep-bodied schooling tetra native to South America. They are incredibly popular for beginners but have a reputation as fin-nippers if kept in too small a group. A proper school disperses their internal bickering and largely prevents them from harassing other tank mates.
Melanotaenia nigrans
The Black-Banded Rainbowfish is a lively, peaceful schooling fish native to northern Australia. Recognized as the first scientifically described species in its genus, they are prized for their dark mid-lateral stripe and energetic swimming behavior. They are highly adaptable, occurring in freshwater streams and occasionally brackish estuaries in the wild.
Rasbora borapetensis
The Blackline Rasbora, often sold as the Red-tailed Rasbora, is a hardy and highly active schooling fish native to Southeast Asia. Recognizable by a bold black lateral line topped with gold and a bright red caudal fin, they are peaceful but energetic. They require plenty of horizontal swimming space in the middle to upper levels of the aquarium and must be kept in schools to feel secure.
Physella acuta
A tiny, fast-moving freshwater snail almost universally introduced accidentally via live aquarium plants. While frequently labeled a 'pest' due to their rapid, prolific reproduction, they are actually an excellent cleanup crew. They consume algae, uneaten food, and decaying plant matter without harming healthy plants. They are hermaphroditic and can self-fertilize, meaning a single snail can start a massive colony.
Hyphessobrycon erythrostigma
A relatively large, deep-bodied tetra known for the distinctive bright red spot on its flank resembling a bleeding heart. They are active schoolers that require plenty of swimming space. While generally peaceful, they can become fin-nippers if kept in numbers fewer than 6 or in an undersized aquarium.
Chilatherina bleheri
A stunning, highly active schooling fish endemic to Lake Holmes (Danau Bira) in Papua, Indonesia. Known for its distinct dual-coloration, with the front half being greenish-blue and the back half turning a vibrant red/orange. They are famously active darters and require long tanks with significant open swimming space and well-oxygenated water.
Astyanax mexicanus
A fascinating, totally blind species originating from limestone caves in Mexico. They are born with eyes that degenerate as they grow. Navigating via their highly sensitive lateral line, they are extremely active and constantly scavenge for food. Best kept in a species tank or with fast-moving, short-finned fish, as their erratic swimming and feeding style can result in accidental fin-nipping of slow tank mates.
Hybrid cichlid (Blood Parrot)
A highly popular man-made hybrid (most commonly a cross between a Midas Cichlid and a Redhead Cichlid). They are known for their bright orange/red coloration, nuchal humps, and distinctive 'smiling' deformed mouths. Due to their mouth anatomy, they cannot bite effectively, which makes them less lethal than purebred Central American cichlids, though they retain strong territorial instincts and will aggressively 'bump' tankmates. They are messy eaters and produce a high bioload.
