Taxonomy & naming
Nemacheilus zonatus was described in 2020 by Lawrence Page, Kristina Pfeiffer, Sitthi Suksri, Zachary Randall and Jonathan Boyd, in a Copeia paper examining variation within what had been called the arrow loach, Nemacheilus masyae. Working through material from across the Mun and Songkhram drainages, the authors found that populations on the Khorat Plateau differed consistently enough in colour pattern and size from typical N. masyae to warrant recognition as a distinct, smaller sister species — N. zonatus.
It belongs to the family Nemacheilidae, the stone and brook loaches, the largest family in the loach superfamily Cobitoidea and one that has been extensively reshuffled as genera such as Schistura, Barbatula and Triplophysa were split from the old broad Nemacheilus/Noemacheilus. N. zonatus was described directly in Nemacheilus and has not been moved since; the Catalog of Fishes is the authority for the current combination.
Morphology
This is a small loach even by Nemacheilidae standards: the original description gives a maximum size of about 1 in standard length, with the holotype measuring 1 in SL — noticeably smaller than its sister species N. masyae, which reaches around 2.5 in SL. The body carries 8 to 12 thin, dusky black bars crossing the back, a yellowish sheen on the cheek and opercle, a dark spot at the base of the caudal peduncle, and reddish colour in the dorsal fin — the banded pattern that gives the species its name.
As in other Nemacheilidae, expect the near-scaleless skin typical of the family, which matters for how sensitive these fish are to medication, and — where present in the genus — a small erectile suborbital spine used defensively. The description does not detail these structures for this species specifically, so keepers should treat them as a family-level expectation rather than a confirmed point for N. zonatus.
Habitat
Nemacheilus zonatus is known from the Mun and Songkhram river drainages on the Khorat Plateau of northeastern Thailand, part of the greater Mekong basin. The type locality is the Pao River, a tributary of the Chi River, at the Route 214 bridge in Kamalasai District, Kalasin Province. Within these rivers it is found in areas of moderate flow near the banks, over sandy substrate — flowing, well-oxygenated lowland river habitat rather than still or heavily vegetated water.
As with many freshly described Nemacheilidae, the full extent of its range and any finer habitat preferences (specific depth, cover, seasonal movement) are not yet well documented beyond the describing paper. Data on this species is genuinely sparse, and that should be stated plainly rather than filled in with guesswork.
Feeding
No feeding studies exist for Nemacheilus zonatus specifically, but its biology fits the pattern typical of small Nemacheilidae in flowing water: a benthic micro-predator picking small invertebrates — insect larvae, worms and tiny crustaceans — off sand and gravel in moderate current. Members of this genus generally do not target large prey or plant matter as a primary food source.
In the aquarium, related stream loaches take small live and frozen foods (bloodworm, brine shrimp, chopped invertebrates) readily and sinking pellets or wafers less readily; flake is often ignored. Until more is known about this particular species, keepers should default to varied small sinking foods rather than assume it will graze algae or accept flake as a staple.
Mating
No courtship or spawning behaviour has been documented for Nemacheilus zonatus. The original description notes that sexual dimorphism was not well developed in the specimens examined, which were collected between November and January — outside of what would likely be the main breeding season for a river loach in a monsoon-driven system. As with the rest of its biology, mating behaviour in this species is undescribed rather than atypical, and any account beyond that would be speculation.
Breeding
Breeding data for Nemacheilus zonatus itself does not exist in the literature. Based on the general pattern for stone and brook loaches, the expected mode is an egg-scatterer that releases eggs over gravel or sand in flowing water, with no parental care — but this has not been confirmed for the species. Nemacheilus zonatus is essentially unknown in the aquarium hobby, so there is no trade or hobbyist spawning record to draw on either.
In the aquarium
Nemacheilus zonatus does not have an established aquarium-keeping record; it is not a hobby staple and specific care guidance for this species has not been published. Extrapolating cautiously from its wild habitat and from the wider genus, it would need cool-to-moderate, clean, well-oxygenated flowing water over a sandy or fine-gravel substrate, and — as with other near-scaleless Nemacheilidae — careful, reduced-strength dosing of any medication.
Given its very small adult size (under 1 in), it would suit a modestly sized tank by loach standards, provided flow and water quality are kept high. Any keeper encountering this species should treat this as informed extrapolation from family-level biology, not a verified care profile.
Conservation
Nemacheilus zonatus has not been assessed on the IUCN Red List; there is no conservation status recorded for it, and we list it here as Not Evaluated rather than guess. As a range-restricted endemic of specific tributaries on Thailand's Khorat Plateau, described only in 2020, it is exactly the kind of small, recently split species that can be overlooked by assessment processes even where its habitat faces real pressure from regional water use and development. There is no evidence of an aquarium trade in this species, so any conservation concern would be habitat-driven rather than collection-driven.