Taxonomy & naming
Pogonoschistura kohchangensis was described by Hugh McCormick Smith in 1945, hence the parenthesised authority. Catalog of Fishes, the governing authority for valid names, and subsequent taxonomic treatments of the group have generally placed it as a junior synonym of Schistura kohchangensis, the ornate tiger sand loach described from the waterfall streams of Koh Chang in the Gulf of Thailand. This kind of synonymy is common in Nemacheilidae, a family that has been repeatedly reshuffled as older catch-all genera such as Nemacheilus and Noemacheilus were split apart; species described independently from geographically close populations were often later found to be the same fish. We keep the requested name Pogonoschistura kohchangensis here rather than silently substitute a different binomial, but readers researching this fish under either name are looking at the same species.
The genus Schistura is itself the largest genus in Nemacheilidae, comprising several hundred species of small, elongate stream loaches distributed from the Indian subcontinent through Indochina and into southern China. The family Nemacheilidae is the largest of the true-loach families by species count, and the great majority of its members — this species included — are narrow-range stream endemics known from only a handful of localities.
This fish was long listed as Schistura deignani; Eschmeyer's Catalog of Fishes now treats that name as a synonym of Pogonoschistura kohchangensis, the valid name followed here.
Morphology
Pogonoschistura kohchangensis is a small, slender, laterally compressed loach reaching only about 2.56–2.95 in standard length — a genuinely diminutive fish even by loach standards. Like other members of its family it shows the classic nemacheilid build: a rounded, scaleless-looking head, small barbels around the mouth for probing the substrate, and a slim body patterned with dark tiger-like bars or blotches over a paler ground colour, the basis for the common name "ornate tiger sand loach."
As in other Cobitoidea, an erectile suborbital spine sits in a groove beneath the eye — a defensive structure shared across the true loaches, though modest in a fish this size compared to the much larger spine of a botiid. The skin carries only minute, deeply embedded scales, leaving the fish functionally naked and, as with all near-scaleless loaches, sensitive to poor water quality, external parasites and strong medications.
Habitat
This species is known from a tight range in the western Gulf of Thailand region: the waterfall and rocky streams of Koh Chang island and the adjacent mainland provinces of Chon Buri, Rayong, Chanthaburi and Trat in southeastern Thailand, extending into the Cardamom mountains of southwestern Cambodia. It is a stream fish through and through, living in fast-flowing, rocky watercourses with strong current and high dissolved oxygen — the kind of clear, tumbling hill stream typical of Nemacheilidae generally.
Reported water conditions are cool-to-moderate and on the softer, slightly acidic-to-neutral side: roughly 68–79 °F, pH 6.0–7.5, with hardness in the 36–215 ppm range. This is not a warm, still, blackwater fish — it is a cool-running, well-oxygenated stream specialist, and any aquarium approximation needs to reproduce that flow and oxygenation rather than default to typical warm tropical community parameters.
Feeding
Pogonoschistura kohchangensis is an omnivorous micro-predator, foraging over the streambed for small aquatic invertebrates — the bloodworms, water fleas (Daphnia) and brine shrimp (Artemia) it is fed in captivity stand in for the insect larvae, small crustaceans and other invertebrates it would pick off rocks and gravel in the wild.
In the aquarium it takes frozen and live foods readily and is likely to ignore dry flake in favour of sinking, meaty foods offered close to the substrate, in keeping with its bottom-foraging habit. As with most small stream loaches, frequent small feedings of appropriately sized live or frozen invertebrate foods suit it better than a single large flake-based meal.
Mating
No reliable account of courtship or spawning behaviour for this species has been documented, and specific external sexual dimorphism has not been described in the sources available. This is typical of Nemacheilidae as a whole: most of the hundreds of Schistura species are known chiefly from museum specimens and brief field surveys, with almost nothing recorded about their reproductive behaviour either in the wild or in captivity.
What can be said follows the pattern for stone and brook loaches generally: these are egg-scattering fish with no pair bond and no parental care, spawning opportunistically in fast-flowing water rather than building nests or guarding broods. Beyond that general pattern, the specifics for this species are simply not documented.
Breeding
Breeding is unreported in the aquarium for Pogonoschistura kohchangensis. Like the overwhelming majority of stone and brook loaches, it scatters eggs over gravel and among stones in fast-flowing water, with no parental care of eggs or fry — but verified home spawnings are essentially unknown, and this species is no exception. Data here is genuinely sparse rather than merely unglamorous.
Aquarists should not expect to breed this fish and should acquire it, when available at all, as wild-collected or incidentally-collected stock rather than farmed fry. Its narrow native range and undocumented captive reproduction both argue for conservative, considered stocking rather than casual acquisition.
In the aquarium
This is a demanding small stream loach, not a beginner's fish. It needs cool-to-moderate, clean, heavily oxygenated water with strong current — a powerhead or spray bar creating real flow, alongside a mature substrate the fish can forage over, is far closer to its native waterfall-stream habitat than a still, warm community tank. Weekly water changes of 30–50% are appropriate given the pristine, fast-turnover water it comes from in the wild.
Being small, scaleless-skinned and drawn from a narrow, specific habitat, it is sensitive to medications and to any decline in water quality; treat cautiously and at reduced strength if disease treatment becomes necessary, and prioritise stable, oxygen-rich conditions over heavy stocking or high temperatures. Given how little is documented about this species specifically, keepers should treat published Schistura/Nemacheilidae care generalities as a starting point rather than a certainty, and watch the fish closely for its own cues.
Conservation
Pogonoschistura kohchangensis has not been formally assessed on the IUCN Red List and carries no conservation category; we record it here as Not Evaluated rather than assign a status the assessment does not support. Its close ally and likely senior synonym, Schistura kohchangensis, is a narrow-range endemic of Koh Chang island and the neighbouring Cardamom mountains, and species with this kind of tight, insular-to-montane distribution are generally more vulnerable to local habitat disturbance even without a formal listing.
As with most Nemacheilidae, no dedicated population monitoring or trade-impact data appears to exist for this species. The responsible position is to flag it as a narrow-range stream endemic worth conservative treatment, without asserting a threat level the data does not support.