Taxonomy & naming
Triplophysa sanduensis was described by Chen and Peng in 2019 in the journal Zootaxa, based on specimens collected from a small cave in Dengguang Village, Zhonghe Town, Sandu County, Guizhou Province, China — the source of its species epithet, sanduensis, "of Sandu." It sits in the genus Triplophysa, part of the family Nemacheilidae, the stone or brook loaches, which the Catalog of Fishes recognises as the largest of the loach families and one that has absorbed many species once placed in the old catch-all genera Nemacheilus and Noemacheilus.
The authors identified T. sanduensis as the sister species to Triplophysa longliensis based on a small mitochondrial COI genetic distance of about 1.9%, placing it among a cluster of narrow-range cave and spring endemics described from the karst landscape of Guizhou in recent years. As with many recently described Chinese Triplophysa, the species is known only from its type series, and no subsequent taxonomic revision or synonymy has been documented.
Morphology
The original description gives a formal anatomical picture rather than a size or colour account aimed at aquarists: dorsal fin rays 8–9, pectoral fin rays 8–9, pelvic fin rays 5, anal fin rays 5, and 4+37 vertebrae, with a complete lateral line running the length of the body. Like other Nemacheilidae it is an elongate, small, softly cylindrical loach adapted for hugging the substrate in current.
A notable point in the description is that T. sanduensis retains functional, apparently normal eyes despite living in a cave — many Guizhou cave loaches described in the same wave of taxonomic work are blind or heavily depigmented, so this species' un-reduced eyes suggest it has not undergone the deep troglomorphic adaptation seen in strict cave specialists. No standard or total length was reported in the original description, and no colour pattern was documented in the sources available here, so size and coloration should be treated as unconfirmed rather than assumed.
Habitat
Triplophysa sanduensis is known only from its type locality: a small cave in Dengguang Village, Zhonghe Town, Sandu County, in the karst uplands of Guizhou Province, southern China. No other populations or localities have been reported. Cave and spring systems in this part of Guizhou are typical habitat for narrow-range Triplophysa, which frequently show single-drainage or single-cave endemism across the region's fragmented karst hydrology.
Water chemistry and temperature for the type locality were not reported in the original description, and no subsequent field or aquarium account is available to fill that gap. Congeneric high-altitude and cave-dwelling Triplophysa from the wider Himalayan-Tibetan and southern Chinese karst region are typically coldwater to cool-water stream or spring specialists rather than warm, still-water fish, which is the safest general expectation here — but for this specific species the numbers are simply not published.
Feeding
No diet data has been published for Triplophysa sanduensis specifically. Nemacheilidae as a family, including the Triplophysa/Schistura group this species belongs to, are overwhelmingly bottom-dwelling micro-predators — foraging over gravel and rock for small invertebrates, insect larvae and other tiny prey items in clear, fast, well-oxygenated water.
In the absence of species-specific data, a keeper would reasonably extrapolate from that family-wide pattern: small live and frozen foods and sinking preparations that reach the bottom, rather than a diet built around flake or surface feeding. This should be treated as an inference from related species, not a confirmed fact about T. sanduensis.
Mating
No sexual dimorphism, courtship, or spawning behaviour has been documented for Triplophysa sanduensis. The original description is a taxonomic account focused on meristic counts and genetic comparison to its sister species and does not address reproductive biology.
Across Nemacheilidae generally, stone and brook loaches show little external dimorphism outside the breeding season and are not known for elaborate courtship; spawning is typically a simple pairing or grouping over gravel in fast water rather than a display-driven process. Whether that general pattern extends to this species is unconfirmed.
Breeding
There is no aquarium or field breeding record for Triplophysa sanduensis — this is unsurprising for a species known from a single small cave and described only in 2019. Stone and brook loaches in Nemacheilidae are, as a rule, egg-scatterers: ripe adults release eggs over gravel or among stones in fast-flowing water with no parental care afterward, and the group as a whole is rarely bred in captivity.
Given the total absence of species-specific breeding data, the honest summary is that T. sanduensis almost certainly follows this family-wide egg-scattering pattern with no parental care, but no confirmed spawning — wild or captive — has been reported, and the species has essentially no history in the aquarium trade.
In the aquarium
Triplophysa sanduensis has no established aquarium history that these sources record; it should be treated as a species that is effectively unavailable and unknown in the hobby, not as a stocking recommendation. Its cave-restricted, single-locality status also raises the question of whether responsible collection or export for the trade should happen at all.
What can be said comes from the wider Nemacheilidae and Triplophysa group: these are scaleless or near-scaleless, cool-to-cold-water, high-oxygen-demanding stream and spring specialists that do poorly in warm, still, low-flow tanks and are sensitive to copper and full-strength medications, as scaleless fish generally are. Anyone who might one day encounter this species in a collection should extend it the same caution given to its congeners — strong flow, high oxygenation, and gentle medication — while recognising that no confirmed care parameters exist for T. sanduensis itself.
Conservation
Triplophysa sanduensis has not been formally assessed by the IUCN Red List and is therefore classified here as Not Evaluated. Its entire known range is a single small cave system in Sandu County, Guizhou — the kind of extremely restricted distribution that, in similar cave-dwelling and spring-endemic Nemacheilidae from the region, often correlates with genuine vulnerability to disturbance, groundwater extraction, or local habitat degradation, even where no formal assessment yet exists.
No trade, export, or population-trend data is available for this species. Given how recently it was described (2019) and how narrow its known range is, any future conservation attention would need dedicated field survey work in the Sandu karst system rather than inference from more widespread congeners.