Taxonomy & naming
Oreonectes guilinensis was formally described in 2019 by Huang, Yang, Wu & Zhao, with the description published in the Journal of Fish Biology in 2020. It sits in the genus Oreonectes, part of the subfamily Nemacheilinae within the family Nemacheilidae — the stone and brook loaches, the largest single family within the true loach superfamily Cobitoidea. The genus name Oreonectes derives from Greek roots meaning roughly "mountain swimmer," a fitting name for a group of loaches confined to the fast, cool streams of karst hill country.
The species epithet guilinensis refers to Guilin, the prefecture-level city in Guangxi Zhuang Autonomous Region whose surrounding limestone landscape gives the fish its home range. Oreonectes is a genus of roughly ten valid species, eight of them endemic to Guangxi, with the remainder reaching into Guangdong and northern Vietnam; several congeners are cave-adapted with reduced eyes, but O. guilinensis is a surface-dwelling species with normally developed eyes, described as phylogenetically close to other regional Oreonectes.
Morphology
This is a small, elongate stone loach: type-series specimens measured 2–3 in standard length, with a mean around 2.5 in and the holotype at 2.5 in SL — a fish that stays well under 4 in. The body is stout for the genus, its width running 14.0 to 16.7 percent of body length, and it is covered in scales rather than being naked-skinned, a genus-level trait that distinguishes it from some other nemacheilid lineages.
The caudal fin is rounded, with 13 to 14 branched rays, and the dorsal fin has six branched rays with its origin set opposite the origin of the pelvic fins. The lateral line is incomplete, reduced to just 4 to 6 pores near the head rather than running the full length of the body — a common reduction in small stream-dwelling nemacheilids. The pelvic fins are short and set well forward of the anus. As in other Nemacheilidae, look for the erectile suborbital spine below the eye and the fine, easily-abraded, near-scaleless-feeling skin typical of the family, both of which matter more for husbandry than for identification in this scaled species.
Habitat
Oreonectes guilinensis is known from the Lijiang River system, part of the Pearl River basin, in the karst landscape around Guilin. Its type locality is a stream at Shigumen Village, Xingping Town, Yangshuo County, Guilin City, Guangxi Zhuang Autonomous Region — the same dramatic limestone-karst country that draws tourists to the Li River, and a landscape riddled with clear, spring-fed, fast-flowing streams and underground drainage.
Unlike the blind, permanently subterranean Oreonectes found in some regional caves, this species is a surface-dwelling stream fish, not a cave specialist. It lives in the clear, cool-to-moderate, well-oxygenated flowing water typical of karst streams in this part of southern China — subtropical rather than tropical, with genus-level ecology pointing to roughly 59–75 °F, cooler and swifter water than the warm, still conditions many aquarists default to for "loaches."
Feeding
Specific dietary data for Oreonectes guilinensis has not been published; this is a genuinely data-sparse point and it is better stated honestly than invented. Its genus and family point clearly enough at the answer: like other stone and brook loaches, it is almost certainly a benthic micro-predator, picking small aquatic invertebrates — insect larvae, small crustaceans, worms — off the streambed, along with some algae and biofilm grazing in the manner typical of Nemacheilidae.
In the aquarium, fish of this ecological type generally take small live and frozen foods (bloodworm, daphnia, brine shrimp) readily and will graze biofilm and algae from surfaces, but tend to ignore dry flake at the water's surface. Any feeding regime for this species should follow that general nemacheilid pattern rather than any species-specific record, which does not yet exist.
Mating
No courtship or spawning behaviour has been documented for Oreonectes guilinensis in the literature reviewed here. The species was described from preserved type material collected for taxonomic purposes, not from aquarium or field breeding observations, and nothing about sex differences, courtship, or spawning triggers has been published. Any description of "typical" nemacheilid mating behaviour for this species would be extrapolation, not fact, so none is offered beyond noting that congeners and the family as a whole are egg-scattering, non-guarding fish with no evidence of pair formation or parental behaviour.
Breeding
As with most stone and brook loaches, Oreonectes guilinensis is not known to have been bred in captivity, and no aquarium spawning has been reported. Based on the family-wide pattern in Nemacheilidae, the expected mode is egg-scattering over gravel and stones in fast-flowing water, with no parental care of eggs or fry — the same pattern documented in better-known Oreonectes and other stone loaches. This species-specific gap is typical for a Nemacheilidae species described only in 2019 from a single stream system: it has essentially no aquarium history, so the honest position is that breeding is rarely or never achieved in the hobby and, for this species in particular, entirely undocumented.
In the aquarium
Oreonectes guilinensis has no meaningful presence in the aquarium trade and is not a species to shop for; what follows is guidance drawn from the ecology of its genus and family rather than from care reports specific to this fish. A stone loach of this kind, if ever kept, would need a cool-to-moderate, well-oxygenated, fast-flowing tank rather than the warm, still setup often assumed for "loaches" — closer to a hillstream biotope than a tropical community tank, with a fine gravel or sand substrate and smooth stones to graze and shelter among.
As with other Nemacheilidae, expect sensitivity to poor water quality and to full-strength medications, and be cautious with copper-based treatments; a maturely cycled tank with a biofilm-rich surface for grazing would suit its likely feeding ecology. Given how narrow its known range is — a single stream system in karst Guangxi — and the total absence of trade or husbandry data, this is a species to appreciate through its scientific description rather than one to seek out for a tank.
Conservation
Oreonectes guilinensis has not been assessed by the IUCN Red List; as a species only formally described in 2019/2020, it is correctly recorded here as Not Evaluated rather than assigned a guessed category. It is known only from its karst stream system near Guilin in the Lijiang River (Pearl River basin), a narrow range that, combined with ongoing development pressure on southern China's karst waterways, would typically warrant conservation attention once a formal assessment is undertaken.
There is no evidence of this species entering the aquarium trade, wild-collected or otherwise, so trade pressure is not a documented concern; the main long-term risk implied by its narrow, single-system distribution is habitat disturbance in its home stream rather than collection. Data remain sparse, and any future study of its population status would be the next meaningful step.