Taxonomy & naming
Schistura beavani was described by Albert Günther in 1868, which is why his name sits in parentheses — the species has since been moved out of whatever genus he originally placed it in. Like a great many South and Southeast Asian stone loaches, it passed through the old catch-all genera Nemacheilus, Noemacheilus and Nemachilus before the Cobitoidea's ongoing taxonomic revision settled it into Schistura, the genus that now holds the great majority of Asia's stream-dwelling nemacheilids.
It belongs to the family Nemacheilidae, the stone or brook loaches — the largest family in the loach superfamily Cobitoidea, comprising hundreds of small, similar-looking species scattered across streams from Anatolia to China. The Catalog of Fishes is the authority for the current combination, Schistura beavani; older literature and some databases may still list it under one of the defunct genera above.
Morphology
This is a small loach, reported to reach roughly 3–4 in depending on the source (Loaches Online gives about 3 in SL, FishBase a maximum of 4 in TL), with the elongated, subcylindrical body typical of Schistura — built for holding position in current rather than for open-water swimming. Like other nemacheilids it carries a small erectile spine below the eye and skin that is effectively naked, with tiny, deeply embedded scales rather than an obvious scaled covering.
Beyond the basic body plan, published morphological detail on this species is thin. It shares the family's general coloration pattern of mottled or barred brown-and-tan camouflage suited to a pebbly streambed, but a full diagnostic description of its markings was not available in the sources consulted here, and we would rather note that gap than guess at specifics.
Habitat
Schistura beavani is native to the Ganges drainage of South Asia, recorded from Bangladesh, India (the states of Meghalaya, Uttaranchal, Uttar Pradesh and West Bengal) and Nepal. FishBase lists the type locality as a river below Calcutta, in the western Ganges delta of South Bengal — though the species as a whole ranges well up into hill-stream habitat across the wider Ganges system.
It lives in fast-flowing, clear streams over pebbly and rocky substrate: shallow, swift hill-stream creeks, riffle areas and the pools between them. This is a fast-water fish that depends on strong current and good oxygenation, not the still or slow-moving lowland water many casual keepers associate with South Asian streams.
Feeding
As a bottom-dwelling stream loach, Schistura beavani is best understood as a micro-predator that forages over gravel and pebbles for small invertebrates — insect larvae, worms and tiny crustaceans washed along in the current. Loaches Online describes it as omnivorous in captivity, taking flake, sinking pellets and frozen invertebrate foods without difficulty.
In the aquarium it should be offered a varied diet weighted toward sinking, meaty foods — frozen bloodworm, brine shrimp and similar — alongside sinking pellets; like most benthic loaches it may largely ignore food that stays at the surface.
Mating
No detailed account of courtship or spawning behavior for Schistura beavani was found in the sources consulted. As with most stone loaches, sexing is likely to rely on subtle differences in body girth in gravid females rather than any strong external dimorphism, but this has not been specifically documented for the species and we note that rather than guess.
Breeding
Loaches Online records no successful aquarium spawnings of this species. In line with the general pattern for Nemacheilidae, the expected mode is an egg-scatterer over gravel and among stones in fast-flowing water, with no parental care — but this remains inferred from the family rather than confirmed for Schistura beavani specifically, and captive breeding data is essentially absent. It should be treated, honestly, as a species that is rarely if ever bred in the home aquarium.
In the aquarium
Schistura beavani wants a river-style setup: strong flow, high oxygenation, a substrate of soft sand with smooth pebbles and rounded stones, and clean, well-filtered water — not a quiet, sluggish community tank. Loaches Online recommends keeping it in a group of five or more; it is described as not territorial and a reasonable mixer with other current-loving stream fish, but it still benefits from the security of numbers typical of small shoaling loaches.
Being near-scaleless, it should be treated with the caution due any nemacheilid when it comes to medication — full-strength treatments and copper-based products are best avoided or used at reduced dose. Water in the 64–77 °F range with a pH of 6.0–7.5 and soft to medium hardness suits it, reflecting its cool, fast-flowing hill-stream origins rather than a warm, still tropical setup.
Conservation
Schistura beavani is assessed as Least Concern on the IUCN Red List. An earlier Bangladesh national assessment had flagged the species as Data Deficient, but the current global IUCN assessment finds no elevated risk.
As a fast-water hill-stream specialist spread across a large, heavily populated river system, the species is potentially exposed to the general pressures on South Asian stream habitats — siltation, water abstraction and pollution — but no species-specific population decline has been documented.