Aquarist Atlas
Aquarist Atlas · the loaches

Loaches

Loaches are the bottom-dwelling specialists of Old-World streams — a huge clade (Cobitoidea) that runs from the beloved clown loach to the eel-like kuhlis, the sucker-bodied hillstream loaches that cling to torrents, the hundreds of little stone & brook loaches, the sand-diving horseface, the coldwater weather loach, and the misnamed Chinese algae eater. They are full of character and full of traps: the botiids must be kept in groups, the hillstreams need cool, fast water, most are scaleless and med-sensitive, and almost none are bred at home. This section is built to the same standard as the cichlid, cory and pleco pages — researched, cited, no Wikipedia, no invented facts.

© Adobe Stock

We cover the true loaches — the superfamily Cobitoidea: the botiids (Botiidae), the kuhlis and spined loaches (Cobitidae), the stone & brook loaches (Nemacheilidae), the hillstream loaches (Balitoridae and Gastromyzontidae) and the Chinese algae eater (Gyrinocheilidae). We leave out the fishes the trade loosely calls “loaches” that are not in this clade: the cyprinid “loaches” and algae-eating “sharks” of the carp family (kept under barbs), the loach cichlids of Lake Tanganyika (kept under cichlids), and the loach catfishes. Following the Catalog of Fishes for valid names, the old catch-all genus Botia has been split into Chromobotia, Yasuhikotakia, Syncrossus, Sinibotia and Ambastaia, and the kuhlis moved from Acanthophthalmus to Pangio — so a fish you bought under an old name may have moved. Two honest threads run through every account: most loaches are scaleless or nearly so, which makes them sensitive to copper and to full-strength medications yet prone to be the first fish to catch ich; and breeding is rarely achieved in the hobby — the clown loaches in shops are hormone-farmed, not home-bred. Read each account before you buy: the social needs and the water are where loaches are usually lost.

A clown loach — an orange, black-banded loach among driftwood
The clown loach (Chromobotia macracanthus) is the icon of the section — and a lesson in loach-keeping. It is obligate-social: kept alone it hides and pines, but in a group of five or more it forms a pecking order, “clicks” audibly and comes out to play. It grows to a surprising 30 cm, lives for decades, and — despite being one of the most-sold loaches — is almost never bred at home. The fish in shops are hormone-induced on farms, not tank-spawned.
A kuhli loach — a slender, eel-like loach banded brown and cream, threading through plants
A kuhli loach (Pangio) — eel-like, nocturnal and a burrower. It wants soft sand to dive into (sharp gravel scrapes its scaleless skin) and cover to hide under by day. Peaceful and social, kuhlis do best in a small group; kept over bare gravel or without hiding places they simply disappear and slowly starve. One of the easiest loaches to lose without ever seeing it die.
A hillstream loach — a flattened, sucker-bodied loach clinging to a smooth stream boulder
A hillstream loach (Sewellia / Beaufortia) — flattened into a living suction cup for life in a mountain torrent. These are a specialist’s fish: they need cool, fast, oxygen-rich water over stone furred with mature biofilm, which they rasp.
A yoyo loach — a silver loach marked with a chain of dark Y-and-O reticulations
The yoyo loach (Botia almorhae), named for the “Y-O-Y-O” chain along its flank — a bold, active botiid that eats pest snails and, like its clown-loach cousin, needs a group to settle. All botiids carry an erectile spine below the eye: a defence that snags nets and can nick a careless hand.
A slender, barbeled loach patterned with a row of dark blotches, resting on a stream rock
A spined loach of the family Cobitidae — the group that gives the loaches their old name. Below each eye sits an erectile suborbital spine it can flick out defensively; it snags nets and can nick a careless hand. Many spined & pond loaches are sand-sifters, and several — the Eurasian spined loaches and the hardy weather (dojo) loach Misgurnus — are temperate, coldwater fish suited to an unheated tank, not the tropics.

Photos © Adobe Stock

1,456 species in the atlas

Grouped by a friendly ecology axis — botiid loaches, kuhli loaches, hillstream loaches, stone & brook loaches, spined & pond loaches, the algae eaters and the odd little families — rather than by the shifting family boundaries, though each account names its current family and authority. Following the Catalog of Fishes and FishBase, Cobitoidea is large and much of it is little-studied (the stone & brook loaches especially), so new accounts are added as they are researched, and the thinly-documented species say so plainly rather than guessing.

Species

1,456 of 1,456 species

Botiid loaches · 60

Family Botiidae — the hobby's iconic loaches: the clown (Chromobotia macracanthus), yoyo (Botia almorhae), zebra (Botia striata), skunk and dwarf chain (Ambastaia sidthimunki) loaches, plus Yasuhikotakia, Syncrossus, Sinibotia and Leptobotia. They are OBLIGATE-SOCIAL — kept singly or in pairs they turn skittish or bully, so they need a group of five or more, where they form a pecking order and "click" audibly. All carry an erectile suborbital spine (it snags nets and can nick a hand), most are near-scaleless and med-sensitive, several eat pest snails, and few are bred at home — the clown loach reaching the trade is hormone-induced on farms, not tank-spawned.

Kuhli loaches · 37

Genus Pangio (Cobitidae) — the eel-like kuhli loaches, slender banded burrowers of soft, shaded forest streams from Indochina through Sundaland. Nocturnal and peaceful, they want fine sand (not sharp gravel) to dive into and plenty of cover; kept over coarse gravel or without hiding places they hide constantly, go underfed and vanish. Social — keep a group. Scaleless and easily damaged, so handle and medicate gently. Very rarely bred in the aquarium.

Hillstream loaches · 256

Families Balitoridae and Gastromyzontidae — the flattened, sucker-bodied "butterfly" and "lizard" loaches (Sewellia, Beaufortia, Gastromyzon, Pseudogastromyzon, Homaloptera, Hemimyzon, Balitora) that cling to rock in fast mountain torrents. They are a SPECIALIST setup: cool, highly-oxygenated, strongly-flowing water over stone coated in mature biofilm/aufwuchs, which they rasp. A few (notably Sewellia lineolata) do spawn in a well-run river tank.

Stone & brook loaches · 854

Family Nemacheilidae — the largest loach family, the small clear-stream loaches (Schistura, Nemacheilus, Acanthocobitis, Yunnanilus and the high-altitude Triplophysa of the Tibetan plateau). Bold, bottom-dwelling micro-predators of cool, fast, oxygen-rich water; many are territorial. This is the data-sparse end of the section: hundreds of species are known from a single stream or a museum lot, so some accounts are necessarily thin. Rarely bred in captivity.

Spined & pond loaches · 235

Family Cobitidae (excluding the kuhlis) — the true/spined loaches: Cobitis and Sabanejewia of Eurasia, the horseface loach Acantopsis (a sand-diving sifter), Lepidocephalichthys, and the temperate weather/dojo loach Misgurnus. All have the erectile suborbital spine that gives the family its name. Several are COLDWATER, not tropical — the dojo is a hardy pond fish that reacts to falling barometric pressure (hence "weather loach"). Sand-sifters that want a soft bed; a handful of the temperate species have been bred, most have not.

Algae eaters · 3

Family Gyrinocheilidae — the Chinese/Siamese "algae eater" (Gyrinocheilus aymonieri) and its two relatives, sold small and cheap as clean-up fish. They ARE loaches, not the true algae-eaters the trade implies, and the sale is a trap: they reach ~28 cm, turn increasingly territorial and aggressive with age, eat less algae as they grow, and may rasp the slime coat of slow tankmates. A modified sucker mouth and separate gill inlets let them cling and breathe in fast water. Not bred at home.

Other loaches · 11

The small, odd Cobitoidea families rarely seen in the trade — Vaillantellidae (the fork-tail loaches, Vaillantella), Serpenticobitidae (the serpent loaches, Serpenticobitis), Barbuccidae (Barbucca) and Ellopostomatidae (Ellopostoma). Southeast-Asian stream fishes, mostly known to specialists and included for completeness; sources are thin and honest.

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