Taxonomy & naming
Nemacheilus cheni was described by Albert William Herre and Show Yung Lin in 1936 in their survey of the fishes of the Tsien Tang (Qiantang) River system, published in the Bulletin of the Chekiang Province Fish Experiment Station. The type locality lies within that river system in Zhejiang Province, eastern China.
Nemacheilidae has been heavily reshuffled since the mid-20th century — many species once placed in the broad, catch-all genus Nemacheilus (sometimes spelled Noemacheilus in older literature) have since been redistributed into Schistura, Triplophysa, Barbatula and other genera as the family's taxonomy has been revised using both morphology and molecular data. Nemacheilus cheni has not been reassigned and remains in its original genus; the Catalog of Fishes is the authority for the currently valid combination.
Morphology
Detailed morphological data for Nemacheilus cheni have not been located beyond the original 1936 description, so specifics of its colour pattern and fin counts are not given here rather than guessed. In general form it will share the build typical of Nemacheilus and its Nemacheilidae relatives: an elongate, sub-cylindrical body, a ventrally flattened head suited to holding position on the streambed, and small barbels around the mouth for feeling out food in the substrate.
Like most true loaches it is expected to carry a small erectile spine beneath the eye — the suborbital spine characteristic of the loach superfamily Cobitoidea — and to have very small, deeply embedded scales that leave the skin close to naked. That near-scaleless skin is a recurring feature across the family and matters directly for how the fish should be handled and, if ever kept, medicated.
Habitat
Nemacheilus cheni is known only from the Tsien Tang (Qiantang) River system in Zhejiang Province, eastern China — a drainage that runs from hilly inland country down to Hangzhou Bay. Fish described from this system and genus are typically stream-dwellers, holding in clear, fast-flowing, well-oxygenated water over gravel, sand and stone rather than in slow backwaters or still ponds.
No specific temperature or water-chemistry data have been published for this species. Based on the genus and its East Asian, temperate-to-subtropical river system, a cool-to-mild flowing-water regime is far more plausible than a warm, still, blackwater one, and this profile treats it accordingly rather than assuming tropical aquarium norms.
Feeding
No dietary study of Nemacheilus cheni has been published. Nemacheilidae as a family are overwhelmingly benthic micro-predators, working the streambed for small invertebrates — insect larvae, worms and tiny crustaceans — rather than grazing algae or browsing plants, and this species is presumed to feed the same way.
If ever kept, a diet built around sinking foods that reach the bottom — small live or frozen invertebrate foods such as bloodworm and daphnia, plus a quality sinking pellet — would suit this feeding style far better than flake, which a bottom-oriented micro-predator may largely ignore.
Mating
No information on sexual dimorphism, courtship or spawning behaviour has been published for Nemacheilus cheni. Data are simply too sparse to describe with any confidence, and this profile will not invent detail that has not been documented.
Breeding
There is no record of Nemacheilus cheni being bred in captivity. Stone and brook loaches (Nemacheilidae) as a family are typically egg-scatterers that release eggs over gravel or among stones in fast-flowing water with no parental care afterward, and that is the pattern this species most likely follows — but it is an inference from the family, not a documented account for this fish specifically. Very few Nemacheilidae species of any kind are bred in home aquaria, and this narrow-range Chinese endemic, with essentially no aquarium trade history, should be assumed to fall into that large majority rather than the rare exception.
In the aquarium
Nemacheilus cheni does not appear to have an established aquarium history, and this profile makes no health or care claims beyond what its biology reasonably implies. As a small stream-dwelling Nemacheilidae species from a flowing East Asian river system, any aquarium attempt would need to prioritise strong water movement, high dissolved oxygen and cool-to-mild temperatures over the warm, still conditions many community fish tolerate.
As with other true loaches, its near-scaleless skin should be assumed sensitive to copper-based medications and full-strength treatments generally, warranting caution and reduced dosing if the fish ever needed treatment. In the near-total absence of published husbandry data, a prospective keeper should treat this as a species for experienced loach keepers researching primary literature, not a fish to buy on impulse.
Conservation
Nemacheilus cheni has not been assessed on the IUCN Red List and is recorded here as Not Evaluated rather than assigned a guessed status. It is known only from the Tsien Tang (Qiantang) River system in Zhejiang Province, China, a pattern of narrow, single-drainage endemism that is common among small Nemacheilidae stream loaches and that leaves such species vulnerable to any localised habitat pressure even without a formal assessment. No information on population trend or specific threats has been published.