Taxonomy & naming
Misgurnus mizolepis was described by the English ichthyologist Albert Günther in 1888 and remains in its original genus, Misgurnus, within the family Cobitidae — the true loaches, named for the erectile suborbital spine folded into a groove beneath the eye that the family carries. Misgurnus is the pond-loach genus, a small group of stout, elongated, near-eel-shaped burrowers spread across temperate and subtropical Eurasia, whose best-known member is the widely traded dojo or weather loach, Misgurnus anguillicaudatus.
The Catalog of Fishes (Eschmeyer, California Academy of Sciences) is the standing authority for the valid combination and treats Misgurnus mizolepis as a distinct, valid species rather than a synonym of the dojo, though the two are frequently confused in the trade and in older hobby literature, both being sold loosely as "weather fish" or "weather loach." No taxonomic revision affecting the genus placement is reflected in the cached sources, so the combination used here — Misgurnus mizolepis Günther, 1888 — stands as given.
Morphology
This is a true loach of family Cobitidae, carrying the erectile suborbital spine that defines the family, tucked beneath the eye and normally invisible until the fish is stressed or handled. The body is long, cylindrical and only weakly compressed, tapering to a rounded tail — the classic burrowing, eel-like build shared with its Misgurnus relatives — and covered in very small, fine scales embedded in mucus-rich, near-scaleless-feeling skin, a detail reflected in the common name "fine-scaled loach." Barbels ring the small, downturned mouth, an adaptation for probing and sifting soft substrate.
Adults reach a substantial 8–10 in, making this one of the larger pond loaches and considerably bigger than most Cobitis species kept in aquaria. As with other scaleless-skinned loaches, that fine scalation and heavy mucus coat make the species sensitive to harsh chemical treatments, a point that matters directly for its care.
Habitat
Misgurnus mizolepis is native to East Asia, recorded from China, Taiwan and Korea, where it inhabits the fine sandy and muddy bottoms of slow-flowing rivers, streams, canals, ponds and paddy-adjacent waters in the midstream and downstream reaches of its range. It is a benthic burrower that digs into soft substrate and buries itself for much of the day, a behaviour that also gives it cover from predators and from temperature extremes.
This is a coldwater to temperate species, not a tropical one: the cache's sourced range of roughly 68–75 °F (68–75°F) sits well below the warmth a typical heated community tank runs at, and the fish does not thrive kept warm. In the aquarium this means a soft, sand-based substrate for burrowing, secure cover such as rockwork, driftwood or dense planting, and a tightly fitted lid or covered top — Misgurnus loaches are proficient escape artists that will find any gap.
Feeding
This is a sand-sifting benthic omnivore and detritivore. In the wild it forages through soft sediment for small invertebrates and organic matter, and in the aquarium it readily accepts flakes, sinking pellets, frozen foods such as bloodworm and mysis, and will happily pick off small snails and other invertebrates it encounters while foraging.
Because it feeds by working through the substrate rather than picking food from open water, it needs a fine, soft bed to forage naturally rather than coarse gravel, and benefits from sinking foods offered after lights-out or scattered near its burrows, since much of its foraging happens low in the tank and out of sight during the day.
Mating
The cache does not document reliable external sexual dimorphism for this species, and no breeding-condition cues are recorded beyond the general pattern seen across the genus. What is well established is the species' unusual sensitivity to environmental change: Misgurnus mizolepis shows erratic, restless behaviour tied to shifts in barometric pressure — the trait behind the "weather fish" name — and this same sensitivity to seasonal and atmospheric cues is thought to play into the timing of spawning activity in temperate Misgurnus species generally.
As a coldwater species, any reproductive cycling would be expected to follow a seasonal, temperature-driven pattern typical of temperate pond loaches — cooler winter conditions followed by a spring rise — rather than the constant warm conditions used to condition tropical loaches, though the cache does not give species-specific spawning triggers for M. mizolepis.
Breeding
Misgurnus mizolepis is a spined/pond loach (family Cobitidae) and, in keeping with the group, an egg-scatterer with no parental care — eggs are released among plants or fine substrate and left unguarded. Several temperate members of this family, including Cobitis, Sabanejewia, and the dojo/weather loach Misgurnus anguillicaudatus, have been pond- or tank-spawned by hobbyists and farmers, typically in spring as water warms after a cool winter, while the tropical Cobitidae such as the horseface loach Acantopsis and Lepidocephalichthys generally have not.
For Misgurnus mizolepis specifically, the cache confirms the species is bred commercially — both as a food fish and for the ornamental trade — in East Asia, but does not specify whether this production relies on natural pond spawning, hormone induction, or both, nor does it document verified spawnings in home aquaria. The honest picture is that this is a farmed species at commercial scale, with the precise breeding mode used by growers not detailed in available sources; parental care is None, consistent with the family.
In the aquarium
Misgurnus mizolepis is a hardy, peaceful, highly social loach that should be kept in a group of three or more — it does poorly and hides constantly when kept alone. Give it a soft, fine sand substrate it can dig into and bury itself in, since burrowing is core behaviour rather than an occasional habit, plus secure cover such as smooth rockwork, driftwood or dense planting. A tight-fitting lid is essential: this is a determined escape artist, especially when startled or when air pressure drops.
Critically, this is a coldwater/temperate species suited to roughly 68–75 °F (68–75°F) in medium-soft to medium-hard water around pH 7.0–8.0 — it should not be kept in a warm tropical community tank, and an unheated setup or outdoor pond in a mild climate suits it far better than a heater set for typical tropical fish. Like other near-scaleless loaches, its fine scalation and mucus-rich skin make it sensitive to copper and to full-strength medications, so treatments should be dosed cautiously. It is also a facultative air-breather, regularly gulping air at the surface, so a lid should still allow it to reach the surface. Size the tank for an adult 8–10 in fish kept in a proper group — this is not a fish for a small tank.
Conservation
Misgurnus mizolepis has not been formally assessed on the IUCN Red List and is recorded here as Not Evaluated (NE). The cached sources describe it as widespread across its native range in China, Taiwan and Korea, with no documented population decline.
The species is farmed commercially at scale across East Asia both for food and for the ornamental trade, which suggests captive production rather than wild collection supplies much of the trade, though the cache does not detail the balance between farmed and wild-sourced fish. As with many widespread East Asian pond and paddy-field species, the main long-term pressures on its habitat are likely to be agricultural water management and pollution in lowland rivers and canals rather than any documented trade-driven decline.