Who fits your tank?

The classic community fish: a tight school of electric-blue stripes that suits planted tanks of 15 gallons and up.

Copper-orange schooling fish with a black wedge; hardy, calm and a good first school for a 15–20 gallon tank.

Colourful livebearers with flowing tails; prefer harder water and breed readily, so plan for fry.

Friendly armoured catfish that sift the sand in groups; need soft substrate and a group of six or more.

Tiny algae grazers for mature planted tanks; keep six or more and supplement with vegetables.

Bright red dwarf shrimp that graze all day and breed in a planted tank; tiny bioload, but fry are snacks for most fish.

The Siamese fighting fish: one male per tank, warm still water, and no long-finned or nippy tank mates.

Tall, graceful cichlids for tall tanks of 30 gallons and up; adults eat neon tetras and shrimp, so stock around them.

Bold, fast barbs that nip fins; great in a busy group of ten, a poor match for slow or long-finned fish.

The best-known algae-eating shrimp, made famous by Takashi Amano; bigger than cherries and a good fit for planted community tanks.

A peaceful tetra with a bright white-over-black stripe; hardier than the neon tetra and an easy fit in any calm community tank.

A hardy, deep-bodied tetra with black 'skirt' fins; easy for beginners, but a small group nips the fins of its tank mates.

A man-made hybrid cichlid with a round body and a beak-like mouth that barely closes; usually gentle and rarely able to swallow tank mates.

A sky-blue Malawi cichlid with a fatty forehead hump; calm and sociable over open sand, but no match for boisterous mbuna.

The go-to glass cleaner: a compact 5-inch pleco with bushy whiskers on the males that needs a cave and vegetables, not just algae.

The most widely kept cory: a tough bronze-green or albino catfish that shoals along the bottom and handles a broad range of water.

The neon's close cousin, with red running the full length of the belly; a soft, acidic-water schooling fish that likes it warmer than neons.

One of the most peaceful barbs: males glow cherry red and leave fins alone, making it great for planted community tanks.

A popular sucker-mouth 'cleaner' that reaches 11 inches and turns aggressive with age, sometimes rasping the slime coat off other fish.

A bold orange-and-black loach that lives 20 years and grows over a foot long, so a proper group needs a 6-foot tank.

The classic store 'algae eater' that grows to nearly two feet, fouls the water and eats less algae with age; a fish for very large tanks only.

A tough Central American cichlid that breeds almost anywhere, and is aggressive enough to attack fish several times its size.

A small blue-and-black striped mbuna with outsized aggression; it attacks much larger fish and is kept only in large, crowded groups.

The 'king of the aquarium': a disc-shaped Amazon cichlid in countless bred colours that needs warm, soft, very clean water.

A bright little gourami popular with beginners; one male per tank, no bettas, and buy carefully, as imported fish often carry an incurable iridovirus.

A graceful Tanganyika cichlid with a lyre tail; one pair grows into a family colony that guards its rocks year-round.

A Central American cichlid with a fiery red throat it flares when threatened; fairly calm for a cichlid but territorial when breeding.

A small, translucent tetra with a glowing orange stripe along its body; peaceful, hardy and at its best in a densely planted tank.

A striped gold mbuna and one of the most aggressive Malawi cichlids; it kills rival males, so plan a crowded harem tank of 55 gallons or more.

The coldwater classic with hundreds of breeds; lives 10–15 years or more, makes lots of waste and needs a roomy, well-filtered tank.

A small, very gentle honey-coloured gourami for calm tanks of 15 gallons with peaceful tank mates.

A silver 'shark' sold at 2–3 inches that is really a food-fish catfish growing past 3 feet; no home aquarium is big enough.

A blazing red West African cichlid that holds its territory year-round and turns extremely aggressive when spawning; best kept as a pair on its own.

A small West African cichlid whose female has a bright belly; a cave-spawning pair digs pits and guards fry along the bottom.

A banded, eel-like loach of about 4 inches that burrows by day and explores the bottom as a group in the evening; needs soft sand.

A tall-finned pleco with a brocade pattern that is sold at 2 inches and grows to about 20, needing a very large tank and heavy filtration.

A sturdy livebearer that needs hard water and plenty of plant food, and does well in slightly brackish conditions.

The smallest Tanganyika cichlid, about 2 inches, living in empty snail shells; a colony carves the sand into tiny fiercely guarded plots.

A big, intelligent Amazon cichlid that learns its owner and begs for food; it swallows any fish that fits and rearranges the tank.

The peacocks of Lake Malawi: brilliant males, grey females, calmer than mbuna and gentle with plants, but they need fine sand to feed.

One of the calmest and most beautiful gouramis, covered in pearly spots; ideal for a quiet planted tank with floating plants.

One of the hardiest corys: a mottled catfish that sifts sand in a group of six and prefers slightly cooler water.

One of the easiest livebearers for beginners: peaceful, colourful and undemanding, happiest in moderately hard water with plants.

An olive 'shark' with red fins, most often sold in its albino form; territorial toward lookalike bottom fish and best kept alone.

A brilliantly coloured dwarf cichlid from the Orinoco llanos that needs warm, very clean water and calm tank mates.

A velvet-black 'shark' with a red tail; beautiful but territorial, chasing lookalike bottom fish and its own kind as it ages.

A large, hardy barb whose males turn bright pink-red when breeding; suits cooler tanks that run without a heater.

A tight-schooling tetra with a bright red nose and striped tail whose colour fades when water quality slips, making it a living warning light.

A bright red, hardy tetra with a notorious fin-nipping habit; needs a big group and no slow, long-finned tank mates.

A calm, large South American cichlid often kept with angelfish and catfish; eats soft plants and any fish that fits in its mouth.

A slim silver fish with a black stripe and one of the few that eats black beard algae; grows to about 6 inches and loves to jump.

A large, very active livebearer whose males carry a sword-shaped tail; it needs a long tank, a lid and hard water.

The most common gourami: hardy, omnivorous and an air breather, though males can turn quarrelsome, especially when spawning.

A small, hardy minnow with red fins that needs no heater; ideal for an unheated tank kept at room temperature.

A lemon-yellow mbuna that is one of the calmest cichlids in Lake Malawi and the usual first choice for a Malawi tank.

A fast, striped danio and one of the hardiest beginner fish; schools near the surface and is happy at room temperature.

The classic blue-and-black rock cichlid of Lake Malawi; one of the more aggressive mbuna, it needs hard alkaline water, rocks and a crowded mbuna-only tank.

An Amazon dwarf cichlid whose males carry a lyre-shaped tail; prefers soft, acidic water and breeds in caves.

A silver 'shark' with black-edged fins, sold as small juveniles but growing to about 14 inches; needs a group and an 8-foot tank.

A large, fully peaceful shrimp that catches floating food with fans on its front legs; it needs strong flow and a mature tank or it starves.

A nocturnal electric fish that glides by rippling a single long fin; it grows to nearly 20 inches and eventually eats small tank mates.

A calm, deep-bodied tetra with a black shoulder patch; males with tall dorsal fins put on harmless sparring displays.

The classic acara with a blue sheen: calm for a 6-inch cichlid, but a keen digger that will swallow any fish that fits in its mouth.

A two-tone rainbowfish, blue-violet in front and orange behind; needs warm, hard, alkaline water and a long tank.

A tiny, pearl-spotted danio with orange fins, the star of planted nano tanks; shy, with males sparring constantly.

The easiest apistogramma: males carry a tall, crest-like dorsal fin, and females guard eggs and fry fiercely in their caves.

A large African tetra with shimmering scales and long, feathery fins on the males; peaceful but skittish, so it needs a roomy tank.

The red-and-white bee shrimp, benchmark of the shrimp hobby; it needs soft, acidic, very stable water, usually on aquasoil and RO water.

A peaceful Amazon eartheater that lives in groups, sifts soft sand all day and asks for a very large tank with clean water.

A large, torpedo-shaped barb with a red line along its body; peaceful but very active, needing a long tank with flow and spotless water.

A 2.5-inch loach with a chain-link pattern that shoals near the bottom and in midwater; fits smaller tanks but eats snails and baby shrimp.

A vivid blue predatory hap from Lake Malawi; not very aggressive, but it eats any fish or fry that fits in its mouth.

An African fish that finds food with a weak electric field and a long trunk-like chin; nocturnal, very sensitive and in need of sand.

A tiny fiery-orange tetra for nano and planted tanks; very peaceful and schools in the middle and upper water.

A tiny, brilliantly coloured cousin of the guppy that suits nano tanks of 10 gallons, but crossbreeds readily with ordinary guppies.

A small puffer with a figure-eight pattern for fresh or slightly brackish water; it loves snails and nips slow tank mates.

A hybrid cichlid with a huge forehead hump that becomes very aggressive with age; the classic one-fish-per-tank pet.

A cheap, see-through North American shrimp whose insides are visible; easy to keep, but short-lived and often hard on fry and shrimplets.

A big, fast danio with blue and gold stripes that needs a long tank, current, very clean water and a tight lid.

A see-through catfish whose skeleton shows through the body; schools in midwater and fades quickly without a group of its own kind.

A golden aquarium form of the Chinese green barb; peaceful, hardy and happy in cooler tanks without a heater.

A bright brackish puffer of about 6.5 inches with a predator's temperament; it needs a roomy tank, salt and hard shelled food.

An easygoing tetra with golden 'headlights' by the eye and at the tail base; a classic, undemanding community fish.

A huge Central American predator with jaguar spots, growing to about 21.5 inches; always territorial and ready to eat any smaller fish.

The famous kissing fish grows to about 10 inches and can live over 20 years; its kisses are really contests for dominance.

A tiny, deep-chested hatchetfish that lives right under the surface; shy and an expert jumper, so a tight lid is a must.

The Japanese rice fish: hardy, peaceful and ideal for an unheated tank or a summer pond, with hundreds of ornamental strains.

A large silvery gourami with a calm but nervous temperament; it needs a roomy tank, floating plants and quiet tank mates.

A small rainbowfish with shimmering blue scales and red fins on the males; shy, schooling and in need of open swimming space.

One of Europe's first aquarium fish: a hardy, striped labyrinth fish that lives without a heater, but males are pugnacious.

The smallest freshwater puffer, an inch of curiosity and attitude; it eats snails, nips fins and rarely suits a community tank.

A big Mexican cichlid speckled with pearly blue spots; it digs, holds a territory for life and treats small fish as food.

A schooling tetra with a black 'hockey stick' stripe and a tail-down swimming pose; hardy, peaceful and good in dim, planted tanks.

A fast, silver, black-spotted catfish with long whiskers, often sold as a bottom cleaner but actually a predator that eats neons and guppies.

The smallest cory at about an inch, schooling in open water as much as on the bottom; a natural fit for nano tanks with shrimp.

The famous Amazon predator, rather nervous in a tank; grows to about 14 inches and needs a huge species-only aquarium.

A slender striped Tanganyika cichlid that lives among rocks, often swimming upside down along cave roofs; keep strictly as one pair.

An ancient air-breathing 'dragon fish' that can live over 30 years, grows to nearly 20 inches and swallows anything that fits in its mouth.

A large, disc-shaped silver fish related to piranhas but plant-eating; skittish, shoaling and able to strip a planted tank bare.

A tough armoured catfish of about 6 inches that gulps air at the surface; peaceful, with males building bubble nests like gouramis.

A fully aquatic frog, most often sold as an albino; easy and long-lived, but a predator that eats any fish it can fit in its mouth.

A spotted cory with bright orange pectoral fins that takes warmer water than most, making it a classic discus-tank companion.

A small, fully aquatic frog of up to 2 inches that can share a tank with peaceful fish, as long as it is target-fed.

An armoured 'talking' catfish with white stripes that is peaceful to fish its size but eats small fish at night and grows to about 9.5 inches.

A yellow-and-brown striped predatory snail kept to control bladder, ramshorn and trumpet snails; it breeds slowly and never becomes a pest.

A big non-annual killifish that patrols the surface and eats anything that fits in its mouth; a jumper that needs a tight lid.

A small left-coiled snail that usually hitchhikes in on plants; a self-fertilising hermaphrodite, so a single one starts a colony.

The spotted, striped cory usually sold as the julii cory; peaceful, easygoing and happy in a group of six over sand.

A bright orange crayfish of about 1.5 inches and the only popular crayfish that fits a planted tank with peaceful fish.

A herbivorous Tanganyika cichlid with dozens of colour forms; fights its own kind so hard that it is kept only in big groups of one form.

A cone-shelled snail that lives in the substrate and stirs it; it breeds without a mate and gives birth to live young, so it fills a tank fast.

A slender 6-inch catfish that looks like a dry stick; slow, shy and easily outcompeted for food by livelier tank mates.

The only known clonal crayfish: every one is female and breeds without males, so a single animal can found a colony of hundreds.

A small African catfish that swims belly-up to pick food from the surface and the undersides of leaves; peaceful and best in a group.

The most popular large aquarium snail; it leaves healthy plants alone and lays its eggs above the waterline, so numbers are easy to control.

A slightly larger, cooler-water relative of the platy; a peaceful livebearer for a community tank with hard water.

The classic flat-coiled snail every fishkeeper knows; it cleans up film and leftovers, breeds easily, and the red form is especially popular.

A big Malawi ambush predator with a giraffe-spot pattern that lies on the sand playing dead, then swallows any small fish nearby.

A hardy but aggressive American crayfish that digs burrows, wrecks plants and eats snails and fish; invasive in many countries and banned in the EU.

A long, cool-water loach that digs in sand and reacts to pressure changes; a good goldfish companion that reaches up to 11 inches.

A large blue-green crayfish with red patches on the claws, up to 8 inches; a predator and plant shredder best kept alone under a tight lid.

A clear, long-armed shrimp from Southeast Asia that looks harmless but is an active predator of small shrimp, snails and fish like guppies.

A small newt with a black back and bright orange belly that needs cool water and a patch of land; its skin is toxic, so it lives without fish.

An energetic silver-and-black loach of about 6.5 inches that excels at eating snails but can tear the fins of slow, long-finned fish.

A large striped ramshorn from South America that grows to about 2 inches and eats almost every plant, plus other snails' eggs.

A small chameleon fish that changes colour with its mood; a calm bottom-dwelling hunter that needs caves and live or frozen food.

A large coldwater pond snail that breathes air at the surface and eats soft plants and other snails' eggs; for coldwater tanks, not tropical planted ones.

The sniper fish that knocks insects down with a jet of water; a 12-inch brackish species that needs a group and air space above the water.

A large, hardy Spanish newt of 6 to 8 inches that is almost fully aquatic, likes cool water and quickly learns to take food from tweezers.

One of the most colourful annual killifish, from drying pools in Mozambique; it lives under a year, while its eggs rest for months in damp peat.

A large, colourful snail with a rabbit-like face from the lakes of Sulawesi; it needs warm, alkaline water and plenty of detritus.

A flat 'butterfly' loach from southern Chinese rivers that clings to rocks and glass and wants cool, fast, oxygen-rich water.

The smallest freshwater crab, with a shell under half an inch; fully aquatic and peaceful, it lives in floating plant roots alongside shrimp.

One of the smallest aquarium fish at under an inch: bright red with a dark stripe, made for planted nano tanks with shrimp.

A small, colourful crab with yellow 'vampire' eyes that lives mostly on land, so it needs a humid paludarium rather than an aquarium.

A small blue-eyed fish with yellow, forked fins; a peaceful top-water school for planted tanks with hard water.

A spotted crab from Lake Matano on Sulawesi that needs warm, hard, alkaline water; aggressive and territorial, it may catch slow fish.

A large Amazon eartheater that sifts sand through its gills; surprisingly peaceful in a group, but needs a very big, warm, soft-water tank.

A Mexican salamander that keeps its feathery gills for life; it needs cool water below 68°F, so it never shares a tropical tank.

A slim pencilfish with a gold and red stripe that hovers near the surface; peaceful and a good match for dwarf cichlid tanks.

A slimmer, more orange cousin of the harlequin rasbora with a 'lambchop' patch; a peaceful school for warm planted tanks.

One of the best-loved non-annual killifish, with a lyre-shaped tail; peaceful, timid, fond of soft water and an excellent jumper.

A bright, calm goby-like fish from New Guinea with an eyespot on the tail; it lives near the bottom in small groups and spawns in caves.

A spotted Lake Tanganyika catfish for cichlid tanks; peaceful in a group but needs hard, alkaline water and may eat tiny fish.

A dwarf cory of about 1.5 inches that stays on the bottom and needs a wide stretch of fine sand rather than a tiny nano tank.

A tiny, under-an-inch scarlet fish for nano tanks; it eats mostly live and frozen foods, and males split the tank into territories.

A silver, diamond-shaped schooling fish from mangroves that moves towards marine water as it grows; it needs a school and a large brackish tank.

A tiny 1.5-inch labyrinth fish that croaks during squabbles; perfect for a soft-water planted nano tank.

A flat, stingray-like loach from Vietnamese mountain streams that needs strong current, cool water and algae-covered rocks.

A black-and-white pleco from the Rio Xingu, one of the most prized aquarium fish; needs warm, clean, fast water and rocky caves.