Taxonomy & naming
Schistura notostigma was described by the Dutch ichthyologist Pieter Bleeker in 1863. It has also long circulated in the older combination Nemacheilus notostigma, and some hobby literature still uses that name; the Catalog of Fishes — the authority followed here — places it in Schistura, the large genus that absorbed most of the Asian species once lumped under the broad, now-obsolete Nemacheilus/Noemacheilus.
It belongs to the family Nemacheilidae, the stone or brook loaches, the largest family in the loach superfamily Cobitoidea and one still being actively revised as older catch-all genera are split along regional and morphological lines. Anyone encountering the name Nemacheilus notostigma in an aquarium guide or older paper should read it as this same fish under its earlier generic placement.
Morphology
Schistura notostigma is a small, slender, cylindrical loach, reported to reach only around 2.5 in in standard length — modest even by the standards of a family built from small, streamlined stream fish. As in other members of the genus it carries the small erectile suborbital spine typical of Cobitoidea, tucked in a groove beneath the eye, and its skin is effectively naked, with the tiny embedded scales typical of nemacheilids offering little protection against harsh water treatments.
Beyond the measurements and family-typical armature captured by the sources consulted here, detailed morphological description of this species — fin ray counts, precise colour pattern, sexual differences in body shape — is sparse in the readily available literature. This reflects its status as a narrow-range stream endemic rather than a well-studied aquarium staple.
Habitat
This species is endemic to Sri Lanka, known from a handful of localities including the Kanneliya Forest, the Gin Ganga drainage, the upper Nanikita Ela, and streams in Sabaragamuwa Province and around Teldeniya. It lives in shallow, fast-flowing, pebble-bottomed streams at higher altitude, the kind of clear, well-oxygenated water typical of stone loaches across their Eurasian range.
Water in these streams runs cool to moderately warm and soft to medium-hard, with FishBase reporting a temperature range of roughly 72–79 °F, a pH of 6.0–8.0, and hardness of 5–12 dH. This is not the warm, still, soft blackwater favoured by many lowland tropicals — it is flowing, well-aerated, mineral-bearing highland stream water, and any aquarium approximation needs to reproduce that current and oxygenation rather than a static tropical setup.
Feeding
In the wild, Schistura notostigma is a benthic micro-predator, browsing the streambed for aquatic invertebrates — caddisfly (Trichoptera) and mayfly (Ephemeroptera) larvae feature specifically in the sources — along with detritus and diatoms scraped from stones. This is a fish built to work a current-swept, invertebrate-rich substrate rather than to graze algae or take food from the water column.
In the aquarium it does well on sinking prepared foods along with frozen bloodworm, brine shrimp and Daphnia, and keepers note it can be a determined, even overeager feeder at meal time. It is unlikely to make much use of floating flake, so food should be offered where this loach actually forages: on and among the substrate.
Mating
No sex-specific external differences or courtship behaviour for Schistura notostigma are documented in the sources available here, and stone loaches in general are notoriously difficult to sex without dissection or close study of the ripe abdomen. Data on this species' reproductive biology in the wild — spawning season, cues, or migratory behaviour — is likewise sparse; it has simply not received the research attention given to larger, more widely traded loach groups.
What can be said follows the pattern for Nemacheilidae generally: these are egg-scattering stream fish with no courtship ritual resembling the cave-guarding or mouthbrooding strategies seen elsewhere in fishkeeping, and no pair-bond or nest is formed.
Breeding
Schistura notostigma is presumed to be an egg-scatterer, broadcasting eggs over gravel and among stones in fast-flowing water with no parental care afterward — the standard reproductive mode across the stone and brook loaches. No successful aquarium breeding of this species has been documented in the sources consulted, and it should be regarded as effectively unbred in captivity.
This is honest rather than disappointing: most Nemacheilidae, this species included, are simply not part of the ornamental breeding pipeline. Specimens in the trade are wild-collected, and a keeper should not expect to reproduce this fish at home.
In the aquarium
This is a small, active stream fish that needs current, not a still community tank. Provide strong water flow and high oxygenation — a powerhead or strong filter outflow helps recreate the pebble-bottomed riffle it comes from — over a substrate of fine sand mixed with smooth pebbles, and add bogwood or slate to create shelters and sightline breaks. Water should be kept cool-to-moderate and well within the 72–79 °F range with a pH of 6.0–8.0; this is not a fish for a warm, soft, still tropical setup.
Being near-scaleless like other loaches, it is sensitive to copper-based medications and full-strength treatments, so any medicating should be done cautiously and at reduced dosage. Sources describe it as somewhat territorial, doing best paired with robust fast-swimming tankmates rather than delicate or sluggish species, and note it can overeat if given the chance, so portioned feeding is worthwhile. Reported lifespan in the aquarium is around 3–5 years.
Conservation
Schistura notostigma is assessed by the IUCN as Near Threatened, reflecting its narrow endemic range restricted to a small number of Sri Lankan stream systems. A species confined to specific highland drainages like the Kanneliya Forest and Gin Ganga catchment is inherently vulnerable to habitat degradation, deforestation and changes in stream flow, even without evidence of a dedicated export-driven collapse.
Specimens reaching the aquarium trade are generally incidental bycatch from broader Sri Lankan freshwater collecting rather than a targeted fishery, meaning the trade is not the primary conservation lever here — watershed protection in its native range is. As with many narrow-range stream endemics in this family, further population data would help clarify trends beyond the current Near Threatened listing.