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Search for fish species by common or scientific name, or use filters to browse by water type, size, temperament, and difficulty.
Found 556 species
Blackfin pygmy skate
Fenestraja atripinna
Fenestraja atripinna is a small, deepwater (upper slope) bathydemersal pygmy skate from the Western Central Atlantic (e.g., Bahamas/Cuba/Florida region) reported from ~310–870 m (often deeper than ~440 m). Biology is poorly known; like other skates it is oviparous (egg cases).
Blackfin slatey
Diagramma melanacrum
This is a big Indo-West Pacific sweetlips/grunt that cruises reefs and hangs in caves, and it gets that cool yellow-and-silver look sprinkled with dark spots plus the really obvious black on the lower tail and the pelvic/anal fins. Juveniles show up in murkier estuary and silty reef areas, then the adults shift deeper and often sit in small groups until they go hunting at night. In aquariums its size is the whole story - it is a public-aquarium kind of fish once grown.
Blackflash ribbonfish
Trachipterus jacksonensis
This is one of those true open-ocean ribbonfish - long, silvery, and super weird-looking in the best way, with a tall red dorsal fin when its in good shape. Its a deepwater, roaming marine species that occasionally turns up nearshore or even in estuaries, but its not something you can realistically keep in a home aquarium.
Black-Lined Loach
Ambastaia nigrolineata
Ambastaia nigrolineata is a little river-loach with two clean black stripes that turns into a really cool barred pattern as it grows. Keep it in a proper gang and you will see all the fun loach stuff - shadowing, clicking, and the occasional goofy "greying out" dominance squabble. It likes clean, well-oxygenated water and lots of nooks to cram into.
Blackspot razorfish
Iniistius dea
This is one of the coolest "knife-bodied" wrasses - it hangs over open sand and, when it gets spooked or wants to sleep, it literally torpedoes straight into the sand. Give it a deep, fine sand bed and it will act totally different (and way more natural) than a typical rock-hugging reef wrasse. Adults are usually shy and cruisy with tankmates, but they are not forgiving about rough handling or sketchy setups.
Blacktip rasbora
Rasbora dorsinotata
This is a slim little Southeast Asian rasbora with a clean dark lateral stripe and a neat black tip on the dorsal fin. In a group it gets way more confident and you will see that tight midwater schooling behavior, especially in a planted tank with some flow.
Blotched catshark
Scyliorhinus meadi
Scyliorhinus meadi is a deepwater little catshark from the western central Atlantic that hangs out way down on the continental slope around 300-600 m. It is got those dark saddle-like blotches and even has tiny spots that can fluoresce yellow under blue light, which is pretty wild for a shark. This is not really an aquarium fish - it is a cold, deepwater species with specialized needs and basically no normal hobby availability.
Blue blanquillo
Malacanthus latovittatus
This is the long, torpedo-shaped tilefish with the blue front end and that bold black stripe down the side. In the wild it hangs over outer reef slopes and will also claim a burrow area, so in a tank you are basically keeping a cruise-missile that also wants a safe "home base" and a tight lid.
Blue discus
Symphysodon aequifasciatus
This is one of the classic wild discus from the Amazon-big, round, and super "cichlid-smart," but way more chill than most cichlids. The coolest part to me is the parenting: the fry actually feed off a mucus layer from the parents' skin for a while, which is just wild to see if you ever breed them.
Blue dorsal Borneo sucker
Gastromyzon ctenocephalus
This is one of the little Borneo hillstream loaches that scoots around like a tiny living suction cup, spending most of its day grazing on biofilm off smooth rocks. The cool part is the fin patterning - the caudal fin has bold pale-blue striping, and they do those quick little territorial "flaring" displays with each other without usually doing real damage. Keep it in a high-oxygen, high-flow setup and it just settles in and does its thing.
Blueband goby
Valenciennea strigata
This is that classic gold/yellow-headed sand-sifting goby with the little blue cheek stripe-always busy, always rearranging your sandbed. In a reef tank it'll spend the day taking mouthfuls of sand, filtering out tiny critters/foods, then "snowing" clean sand back out, and it'll usually claim a burrow area (often as a pair in the wild). It's super cool behavior-wise, but you really do need a mature tank with a proper sandbed and a lid because they can jump.
Blunt-snouted grenadier
Ventrifossa obtusirostris
This is a deep-sea rattail (grenadier) from the southeastern Pacific, living way down on the slope around 750-800 m deep. It is a long, tapering, big-headed macrourid that tops out around 30 cm, and its short, blunt snout is basically the whole idea behind the species name.