Taxonomy & naming
Nemacheilus cleopatra was described by Jörg Freyhof and Dmitry Serov in 2001, part of a wave of species-level revisions that untangled the previously lumped Southeast Asian stone loaches once known broadly as "Noemacheilus" or "Nemacheilus" species-complexes. The type locality is the Ba (Da Rang) River drainage in central Vietnam, and the species remains classified in Nemacheilus within the family Nemacheilidae — the stone or brook loaches, by far the largest family in the loach superfamily Cobitoidea.
The genus Nemacheilus has been repeatedly split and re-split as ichthyologists resolve the Cobitoidea using both morphology and genetics, with many species once called Nemacheilus or Noemacheilus now placed in Schistura, Barbatula, Triplophysa or other segregate genera. Catalog of Fishes (Eschmeyer), the standing authority for valid names, retains cleopatra in Nemacheilus; this profile follows that placement.
Morphology
This is a small, slender loach, reaching a documented maximum of about 3 in standard length — modest even by the standards of the stone-loach family. Like its Nemacheilus relatives it has an elongated, subcylindrical body suited to holding position against current, and a pattern of 9–13 vertically elongated dark blotches along the flanks paired with 8–11 saddle-like markings along the dorsal midline, an arrangement the original description likened to an elegant, banded appearance — reportedly the inspiration for naming it after Cleopatra.
As in other Nemacheilidae, the skin carries small or embedded scales rather than the larger, more armoured scaling of some other fish families, which in the family generally translates to sensitivity when it comes to disease treatment. Detailed anatomical data beyond the type description — fin ray counts, precise scale details, presence and shape of a suborbital spine in this particular species — is not documented in the sources available here, so it is best treated as data-sparse rather than assumed to match its relatives point for point.
Habitat
Nemacheilus cleopatra is known from the Ba (Da Rang) River system of central Vietnam, a tropical freshwater drainage. FishBase records it as benthopelagic, living on the bottom in fast-flowing water over open sand substratum — the classic stone-loach habitat of clear, well-oxygenated, current-swept river channels rather than still or heavily vegetated water.
Beyond that single documented locality and habitat description, the species' finer-grained ecology — seasonal water level changes, associated vegetation, exact depth range — has not been recorded in the available literature. As with many single-drainage Southeast Asian stone loaches, it should be treated as a genuine local endemic until further survey work says otherwise.
Feeding
No species-specific feeding study is available for Nemacheilus cleopatra. Based on its fast-flowing, open-sand habitat and its placement among the stone loaches, it is reasonable to expect it forages as a bottom-dwelling micro-predator, picking small invertebrates — insect larvae and other small aquatic prey — from the substrate, in the manner typical of the genus. This is an inference from habitat and family, not a documented diet, and should be read as such.
In the aquarium, a stone loach of this type would be expected to take small live and frozen foods (bloodworm, brine shrimp, chopped invertebrates) and sinking prepared foods offered at the substrate; it is unlikely to compete well for food at the surface or in mid-water.
Mating
No courtship or spawning behaviour has been documented for this species specifically. General accounts of Nemacheilus reproduction describe free spawning without any pairing ritual beyond release of eggs and milt into the water column over gravel, timed to seasonal rains — but no observation confirms this pattern in cleopatra itself, and no data on sexual dimorphism (size, fin shape, or coloration differences between males and females) has been recorded for the species.
Breeding
As in most Nemacheilidae, breeding for this species is best described from the wider genus rather than from any account specific to cleopatra: an egg-scatterer that releases eggs over gravel in fast-flowing water with no parental care, with spawning in related species reported to coincide with the rainy monsoon months. There is no record of Nemacheilus cleopatra being spawned or reared in the aquarium, and no husbandry literature addresses it. This is a data-sparse species in every practical respect, and any breeding attempt would be exploratory rather than following an established protocol.
In the aquarium
Nemacheilus cleopatra is essentially absent from the hobby literature — it does not appear to be an established aquarium fish, and no dedicated care profile exists among the sources consulted here. What can be responsibly extrapolated from its wild habitat and its place among the stone loaches: a small (around 3 in), current-loving fish that would need cool-to-warm, clear, fast-moving, well-oxygenated water over a sandy or fine-gravel substrate, rather than a still, warm community tank. Stone loaches in general are scaleless or near-scaleless and correspondingly sensitive to copper-based and full-strength medications, a point worth keeping in mind for any Nemacheilus species that does turn up in trade.
Given the near-total absence of documented husbandry, this profile does not recommend specific tank parameters as established fact — a prospective keeper should treat any specimen as a poorly known, likely wild-collected stream fish and research further before purchase.
Conservation
The IUCN Red List assesses Nemacheilus cleopatra as Least Concern, per FishBase's summary of the 2010 assessment. Beyond that status, no population trend, threat assessment narrative, or trade data is available in the sources consulted for this profile. As a single-drainage endemic of the Ba (Da Rang) River system in Vietnam, it would in principle be vulnerable to the same broad pressures — damming, sedimentation, water extraction — that affect many Southeast Asian river stone loaches, but no source here documents such pressures acting on this species specifically, so none are asserted.