Freshwater aquarium fish

235 species across 13 groups. Every profile carries adult size, water requirements, group needs and behaviour with the evidence behind each value — including, where it applies, an explicit note that AquariumHQ does not hold one.

Browse by type

Grouped the way the trade and the hobby group them rather than by family, because a hatchetfish is a characin and somebody looking at tetras will meet one. Each group page separates its species by adult size.

Cichlids

42 species

The most behaviourally complex fish in the hobby and the ones most often bought at a tenth of their adult size. Ranges from a 5 cm Apistogramma to a 35 cm Oscar, with territory and breeding aggression as the axis that decides almost every stocking question.

Catfish

30 species

Bottom-dwellers spanning corydoras that sift sand, loricariids that rasp wood, and river predators sold at a fifth of their adult length. Substrate and feeding time matter more here than water chemistry.

Tetras and other characins

29 species

Shoaling South American and African fish sold as the default community stock. Most need larger groups than they are sold in, and several of the ones with the mildest reputations are persistent fin-nippers.

Danios and rasboras

26 species

Small, fast, open-water danionins. Almost all of them measure their tank in horizontal run rather than volume, and several of the smallest want blackwater rather than the community conditions they are sold into.

Gouramis and other labyrinth fish

18 species

Air-breathers that must reach a still surface, which makes the space above the water a husbandry requirement rather than a detail. Ranges from a 3 cm sparkling gourami to a 30 cm kissing gourami.

Barbs

15 species

Active cyprinids with a fin-nipping reputation that is deserved by some and not by others. Several are subtropical and suit an unheated room better than a heated tank.

Rainbowfish and blue-eyes

15 species

Australasian atheriniforms whose males colour up only in competition, and often only after a year or two. Most want hard alkaline water, which is the opposite of what their tankmates are usually given.

Loaches

14 species

Social bottom-dwellers that need numbers, soft substrate and more caves than fish. Most are long-lived, several are sensitive to standard-dose ich medication, and the trade names cover more species than the labels admit.

Livebearers

11 species

Fish that give birth to free-swimming young. The Poeciliids are the familiar ones; the goodeids nourish their young internally, come from a cooler climate, and include species close to extinct in the wild.

Killifish

10 species

A group defined by how it survives water that disappears. Some are annual and live about a year by design; others are not, and the difference decides whether a death at twelve months is a failure or a life.

Oddballs and unusual species

9 species

Fish that do not fit the community shelf: obligate air-breathers, electrolocating hunters, surface ambush predators and transparent perches. Most are sold small, several are wild-caught, and each poses a husbandry question the rest of the catalogue does not.

Gobies and gudgeons

8 species

Perching bottom-dwellers, several of which are sold as brackish animals and are not. Males hold small display territories and colour up only where there is another male to colour up at.

Puffers

8 species

Beaked predators whose teeth grow continuously and are worn down by crushing shelled prey, which makes a snail supply a husbandry requirement. Genuinely freshwater species only — the brackish and marine ones are outside AquariumHQ's scope.

How the catalogue divides by adult size

Adult size is the single most useful thing to know before buying and the one most often left off a shop label. Every group page below separates its species along these bands.

Band	Species	What it means
Nano — under 4 cm	29	Small enough for tanks under 60 cm, and usually needing larger groups than their size suggests.
Small — 4 to 8 cm	95	The core of most community tanks.
Medium — 8 to 15 cm	66	Needs real swimming length. Frequently sold as juveniles into tanks that will not suit the adult.
Large — 15 cm and above	45	Specialist tanks. Check the adult size and the lifespan before buying.

Sizes are the adult size AquariumHQ holds for the species, not the size it is sold at. Where a maximum recorded length and a typical adult size differ, the profile keeps them apart rather than publishing the larger figure as a planning number.

Not a fish?

Shrimp, snails, crayfish and crabs are catalogued separately under invertebrates. Compatibility between the two groups is assessed by the same engine and the same stored traits, so a pairing page exists wherever one is worth publishing.