Taxonomy & naming
Smithstura poculi was described by the American ichthyologist Hugh M. Smith in 1945 as Noemacheilus poculi, part of his extensive work cataloguing the freshwater fishes of Thailand. Like a great many Indochinese nemacheiline loaches, it was swept up in Maurice Kottelat's major 1990 revision of the group, which redistributed species out of the old catch-all genus Noemacheilus (and the closely related Nemacheilus) into more tightly defined genera including Schistura. The Catalog of Fishes — the authority for valid names — lists the species today as Smithstura poculi (Smith, 1945), the parentheses signalling that Smith's original combination has since changed.
The species sits in Nemacheilidae, the stone and brook loach family, which is by far the largest and most species-rich family of loaches and one of the largest families of freshwater fish overall. Older literature and some database entries may still carry the name under Noemacheilus poculi; that name and Smithstura poculi refer to the same fish.
This fish was long listed as Schistura poculi; Eschmeyer's Catalog of Fishes places the species in Smithstura, and the current combination Smithstura poculi is followed here.
Morphology
Smithstura poculi is a slender, elongate loach, small even by the standards of its genus: FishBase records a maximum standard length of just 2.3 in, with other sources putting total length nearer 3.1–3.9 in. Its colour pattern is diagnostic within the genus — a series of dark bars crosses the body, with the bars anterior to the dorsal fin noticeably thinner than those behind it, and the thin anterior bars are often fused in pairs at their upper ends where they meet the back.
As in other Schistura, the body is covered only in tiny, deeply embedded scales, leaving the skin functionally naked — a trait shared across the family and one with real consequences for medication sensitivity. Below each eye sits the erectile suborbital spine typical of the Cobitoidea, a defensive structure kept folded away in a groove of skin except when the fish is disturbed or handled.
Habitat
The species is native to fast-flowing streams across three of mainland Southeast Asia's major river systems: the Chao Phraya basin (its type locality is a stream draining Doi Angka, now Doi Inthanon, in the upper Mae Nam Ping drainage of northern Thailand), the Mekong basin in Laos and Thailand, and the Salween basin along the Thailand-Myanmar border. FishBase describes its habitat as brooks and streams with swift current running among pebbles, stones and boulders, as well as creeks with more moderate current and clear water.
This is a cool-to-moderately-warm, well-oxygenated, clear-running stream fish, not a still-water or blackwater species. In the aquarium that translates to a preference for flowing, highly oxygenated water over a coarse substrate of gravel, pebbles and stones rather than the soft mud or leaf litter favoured by many lowland loaches.
Feeding
As a benthic micro-predator of fast, clear streams, Smithstura poculi forages along the bottom for small invertebrates — insect larvae, tiny crustaceans and other invertebrate prey that live among the stones and pebbles of its home water. This diet, typical of stream-dwelling nemacheilids, favours meaty, sinking foods over flake or plant matter.
In the aquarium the Loaches Online profile notes it readily accepts sinking pellets, bloodworm and brine shrimp. A keeper should offer these on the bottom, where the fish naturally hunts, rather than relying on foods that stay in the water column; flake that drifts uneaten will simply go to waste on a fish built to feed head-down among the substrate.
Mating
No external sexual dimorphism has been documented for this species in the sources consulted, and detailed courtship behaviour has not been described. FishBase notes only that examined females carried ripe ovulae, confirming the species reproduces on a typical seasonal cycle in the wild, but does not describe spawning behaviour or site selection in detail.
As with most stone and brook loaches, reproduction in Smithstura poculi is best understood as tied to the natural rhythms of its fast-flowing home streams rather than to any elaborate pairing ritual — there is no evidence of the cave-guarding or mouthbrooding strategies seen in other fish groups, and nothing in the available sources suggests otherwise here.
Breeding
Breeding in the aquarium is not documented for Smithstura poculi. Like the great majority of Nemacheilidae, it is presumed to be an egg-scatterer that releases eggs over gravel and among stones in fast-flowing water, with no parental care afterward — the general pattern for the family — but no aquarium spawning has been reported in the sources available here.
This is honestly a data-sparse area for the species: it is a stream specialist known mainly from wild collections and museum records rather than from the hobby, and nothing in the cache indicates it has ever been bred by a hobbyist. Keepers should not expect to spawn this fish and should treat any wild-collected or imported stock as effectively unrepeatable in a home setup.
In the aquarium
Smithstura poculi is a small, hardy-looking stream loach suited to a specialist biotope tank rather than a general community. Its native water is swift and richly oxygenated, so it does best with strong flow — a powerhead or spray bar aimed along the bottom — over gravel, pebbles and smooth stones that mimic its home substrate, plus cover in the form of rockwork it can retreat into. Loaches Online notes it is territorial and needs adequate hiding spots to settle in.
Being a scaleless loach, it shares the family's sensitivity to copper-based medications and to full-strength doses of many standard treatments; half-doses and gentle, loach-safe products are the safer route if disease treatment becomes necessary. Water should be kept cool to moderate rather than tropical-warm — the Loaches Online range of roughly 64–77 °F reflects its swift, clear-stream origin — and soft to medium-hard with a pH in the neutral-to-slightly-acidic range. This is a fish for keepers building a genuine fast-water stream setup, not a catch-all bottom-cleaner for a standard tropical community.
Conservation
The IUCN Red List assesses Smithstura poculi as Least Concern, an assessment dated 2011. The species is known from a reasonably broad spread of streams across the Chao Phraya, Mekong and Salween basins in Thailand, Laos and Myanmar, which likely supports its low-concern status despite its restriction to fast-flowing habitats.
As with many small stream loaches of the region, the more relevant long-term pressures are habitat-scale rather than trade-driven: damming, deforestation of watershed catchments and general degradation of clear, fast-flowing stream habitat across mainland Southeast Asia. There is nothing in the available sources to suggest this species is targeted by the aquarium trade in any volume; it appears to be known chiefly from scientific collection rather than commercial export.