Taxonomy & naming
The species was described in 1979 by Wu and Chen as Nemachilus rotundiventris, part of the broad wave of Chinese ichthyological description work of that era. Nemachilus (also spelled Noemacheilus in older literature) was for decades a catch-all genus for Eurasian stone loaches; the group has since been extensively split, and the Catalog of Fishes — the authority followed here for valid names — now places this species in Triplophysa, the large, mostly high-altitude Asian genus that absorbed much of the old Nemachilus material from the Tibetan Plateau and its margins. The combination in use today is therefore Triplophysa rotundiventris (Wu & Chen, 1979), with the parenthetical authority marking the change of genus since the original description.
The family placement is Nemacheilidae, the stone and brook loaches, now recognized as a family separate from the true loaches (Cobitidae) and the botiids (Botiidae). Triplophysa itself is one of the most species-rich loach genera, radiating across the Tibetan Plateau, the Himalaya and neighbouring drainages of China and Central Asia — a group where taxonomic revision is ongoing and where a great many species, this one included, are known from only one or a few original collections.
Morphology
Triplophysa rotundiventris is a small loach, reported to reach around 3 in in standard length — modest even by the standards of stone loaches, and well short of the size of the botiids and larger Cobitidae covered elsewhere in this atlas. Detailed morphological description in the accessible literature is limited, but as a member of Nemacheilidae it shares the family's general build: an elongate, cylindrical to moderately compressed body, a flattened head and underslung mouth suited to feeding from the stream bed, and the barbels typical of the group used to probe substrate for food.
Unlike the botiids, nemacheilids such as Triplophysa lack the prominent erectile suborbital spine that gives the botiid family its old name of "spined loaches"; instead they rely on a cryptic, streamlined body and a fast dart-and-hide response to avoid predators in open, current-swept water. Like virtually all loaches the skin carries small or reduced scales rather than heavy armour, which matters directly for how the species should be handled and medicated if it is ever kept — treat it as scaleless and sensitive rather than assume otherwise.
Habitat
The species is known from tributaries of the upper Yangtze River within the Yushu Tibetan Autonomous Prefecture of Qinghai, China — the type locality is a tributary called the Jiegu He — with an additional record from the Mount Namjagbarwa region of Tibet. This places it firmly on the eastern Tibetan Plateau, one of the highest and coldest freshwater environments occupied by any loach genus, and squarely within Triplophysa's core range.
FishBase classifies it as a subtropical, benthopelagic freshwater fish of clear, fast-flowing streams — the classic nemacheilid habitat of cool, well-oxygenated water running over stone and gravel substrate at altitude. Nothing in the available sources suggests this is a warm, still-water species, and given its high-altitude Tibetan Plateau range and its similarity to congeners such as Triplophysa stoliczkai, which is kept at 61–68 °F in the rare cases it appears in captivity, it should be treated as a genuinely cold-water fish rather than defaulted to tropical aquarium temperatures.
Feeding
Specific dietary data for Triplophysa rotundiventris has not been located, but its trophic level of 3.1 as recorded by FishBase places it as a micro-predator, consistent with the general pattern for stone loaches: foraging over the stream bed for small aquatic invertebrates, insect larvae and crustaceans, with algae and biofilm taken incidentally in some populations. This is a fish built to hunt live prey off cobble and gravel in moving water, not to graze flake at the surface.
Were it ever kept, a diet mirroring that wild pattern — small live or frozen foods such as bloodworm and daphnia, plus sinking foods that reach the bottom before larger tankmates intercept them — would be the appropriate approach, following the general feeding pattern documented for its stone-loach relatives rather than any species-specific record, which does not exist in the sources available.
Mating
No courtship or spawning behaviour has been documented specifically for this species. General accounts of stone loach reproduction describe territorial males and comparatively elaborate courtship ahead of spawning, timed to rising water temperatures in late spring to early summer as meltwater and rain lift flow in these high-altitude streams — but this is family-level information, not a confirmed account of Triplophysa rotundiventris itself, and should be read as background rather than established fact for this species.
Given how little is recorded about the species even taxonomically, it is honest to say that its reproductive biology is effectively unstudied outside of what can be inferred from its relatives and its family.
Breeding
As with other stone and brook loaches, Triplophysa rotundiventris is presumed to be an egg-scatterer, releasing eggs over gravel and among stones in fast-flowing water with no parental care afterward — the standard nemacheilid pattern. There is no record of this species being bred, or even kept, in the aquarium hobby, and the primary literature on it is thin enough that even its wild breeding season and fecundity have not been documented in the sources reviewed here.
This is one of the many hundreds of stone loaches that exist almost entirely as museum specimens and taxonomic records rather than as animals anyone has observed spawning, whether in the wild or in captivity — data sparse is the honest and complete answer for this section.
In the aquarium
Triplophysa rotundiventris is not established in the aquarium trade and there is no evidence it has ever been kept or offered for sale; this entry exists for completeness of the Tibetan Plateau stone-loach fauna rather than as a stocking recommendation. If it were ever to appear, its high-altitude origin argues strongly for cold-water rather than tropical treatment — likely in the same range as its better-documented congener Triplophysa stoliczkai, around 61–68 °F — paired with strong flow, high dissolved oxygen, a gravel or stone substrate, and the general loach caution that near-scaleless skin means sensitivity to copper and full-strength medications.
At a maximum recorded size of around 3 in SL it would be a small, unassuming fish, and like most obscure Nemacheilidae it would need a keeper prepared to replicate cool, current-swept, high-oxygen stream conditions rather than a standard heated community tank.
Conservation
Triplophysa rotundiventris has not been evaluated by the IUCN Red List, so it carries no conservation category here — Not Evaluated is recorded rather than guessed. FishBase notes only medium resilience, with a minimum population doubling time of 1.4 to 4.4 years, but no population trend or threat data is available.
As a species known from a narrow set of high-altitude Yangtze tributary localities on the Tibetan Plateau, it fits the broader pattern for the region's stream-endemic loaches: poorly surveyed, likely range-restricted, and vulnerable in principle to the pressures facing Tibetan Plateau headwaters — damming, water diversion and climate-driven changes to glacial meltwater regimes — even though no formal assessment documents the scale of any such threat for this particular species.