Taxonomy & naming
Physoschistura dikrongensis was described in 2012 by Lokeshwor and Vishwanath, two ichthyologists working on the fish fauna of Northeast India, in a paper covering the loaches of the region. The species epithet dikrongensis refers directly to its type locality, the Dikrong River, a tributary within the Brahmaputra drainage in Arunachal Pradesh — the classic pattern for narrow-range Himalayan stream loaches, whose names often simply record the stream they were found in.
The genus Physoschistura sits within Nemacheilidae, the stone and brook loach family, whose generic boundaries in the Himalayan region have been repeatedly revised as researchers split the old, catch-all Nemacheilus and Noemacheilus into narrower genera such as Schistura, Physoschistura, Triplophysa and Paracobitis. The Catalog of Fishes is the governing authority for the valid combination, and it currently stands as Physoschistura dikrongensis; no synonymy or reclassification affecting this species has surfaced in the available sources, so the original combination is retained here.
Morphology
This is a small loach, reaching only about 2 in standard length according to FishBase — among the smaller members of an already diminutive family. The body is oval in cross-section, typical of the genus, with a dorsal fin bearing roughly 8½ branched rays, a forked caudal fin with 8 plus 7 branched rays, and a comparatively short anal fin of four simple rays. Males carry a suborbital flap, a fold of skin near the eye that in many nemacheilids sits alongside — or stands in for — the more familiar erectile suborbital spine of botiid loaches, and the species also shows a well-developed axillary pelvic lobe, a small flap at the base of the pelvic fin used in some nemacheilid taxonomy to help separate closely related species.
Like other stone loaches, Physoschistura dikrongensis is essentially scaleless to the touch, its skin bearing only tiny, deeply embedded scales rather than the more obvious scaling of many aquarium fish. Beyond these characters, the published record does not describe its colour pattern or banding in detail, so this profile does not speculate on markings beyond what has actually been recorded.
Habitat
The species is known only from the Dikrong River, a hill-stream tributary of the Brahmaputra system in Arunachal Pradesh, in the eastern Himalayan foothills of Northeast India. Streams of this kind run cold and fast off the mountains, over rocky and gravel beds, and carry heavy dissolved oxygen from constant turbulence — exactly the setting the wider genus Physoschistura is associated with across the Himalayan hill-stream belt, alongside related Physoschistura populations recorded from Darjeeling, Assam and other parts of Northeast India.
Water temperature at this elevation is cool rather than tropical-warm, on the order of roughly 66–73 °F based on conditions reported for related Himalayan Physoschistura, with a substrate of stone and gravel and a current strong enough to keep the bottom clear of silt. No published pH reading exists for the type locality; a neutral-to-slightly-acidic reading typical of clear Himalayan hill-streams is a reasonable inference but not a measured fact, and is noted here as such rather than presented as confirmed.
Feeding
As with most Nemacheilidae, Physoschistura dikrongensis is a benthic micro-predator, and FishBase's trophic-level estimate of 2.8 places it as a secondary consumer feeding on small animal prey rather than algae or detritus. In the wild this means picking small aquatic insect larvae, crustaceans and other invertebrates out of the gravel and stone surfaces of fast riffles.
No aquarium feeding data has been published for this species specifically, but the pattern holds firmly across the genus: a fish built to hunt small live prey in current will generally accept small sinking live and frozen foods — bloodworm, brine shrimp, chopped invertebrates — far more readily than flake, which tends to float past a bottom-hugging stream loach before it can be eaten.
Mating
Nothing has been published on courtship or spawning behaviour in Physoschistura dikrongensis itself. Nemacheilid stone and brook loaches as a group are egg-scatterers rather than pair-forming or nest-guarding fish, releasing eggs over gravel and stones in flowing water with no parental involvement, and there is no reason from the available record to expect this species to differ. Beyond that general pattern for the family, the specifics of pairing, timing or spawning triggers for this particular species are simply unrecorded.
Breeding
Physoschistura dikrongensis has not been bred in captivity as far as the available sources record, and this is consistent with the wider genus: small, narrow-range Himalayan stone loaches are rarely if ever kept or spawned in home aquaria. What can be said follows the general Nemacheilidae pattern rather than species-specific observation: an egg-scattering strategy over gravel and stones in fast-flowing water, with no parental care of eggs or fry.
Given how little is known even about this species' basic ecology outside its type description, any aquarium breeding account beyond that general family pattern would be speculation, and none is offered here.
In the aquarium
This species is not established in the aquarium trade and there is no hobbyist literature describing it in captivity, so care recommendations here are inferred from its biology and from the wider Physoschistura and hillstream-loach group rather than from tested aquarium experience. A cool-to-mild temperate setup rather than a standard tropical tank would be called for — cooler water, strong current and heavy oxygenation, closer to the requirements described for hillstream loaches generally than to a warm, still community tank.
A stony, gravel substrate with good flow across it would replicate the riffle habitat the species is adapted to, and small live or frozen invertebrate foods offered where the current can carry them to a bottom-feeding fish would suit its micro-predator diet. As with other nemacheilids, its near-scaleless skin means any medication should be approached cautiously, at reduced strength, with copper-based treatments avoided. In practice, this is a species that belongs in the realm of specialist or research interest rather than the general trade — anyone encountering it should treat the near-total absence of husbandry data as a reason for caution rather than improvisation.
Conservation
Physoschistura dikrongensis has not been assessed by the IUCN Red List and is recorded here as Not Evaluated rather than assigned a guessed category. It is known only from the Dikrong River in Arunachal Pradesh, and a species restricted to a single hill-stream system is inherently vulnerable to anything that degrades that specific watercourse — deforestation, damming, sedimentation or pollution in the Brahmaputra's Himalayan tributaries — even though no formal assessment or population trend has been published to confirm or quantify that risk.
The honest position, given the sources available, is that this is a narrow-range Himalayan endemic about which almost nothing beyond its original description and a basic FishBase entry has been documented, and any statement about its population trend or trade pressure would go beyond what is actually known.