Taxonomy & naming
Danio nigrofasciatus was described by Francis Day in 1870, originally from specimens collected in northern Myanmar. The Catalog of Fishes (Eschmeyer, the authority for valid names) records the valid combination as Danio nigrofasciatus (Day, 1870), the parenthetical authority reflecting its transfer into Danio from Day's original genus assignment.
The species belongs to the true danio assemblage within the genus Danio, a diverse group of small, active, horizontally patterned or spotted cyprinids distributed across South and Southeast Asia. No synonyms or old genus combinations are noted in the available record for this species; it has been treated under Danio throughout most of its documented history. The specific epithet nigrofasciatus is descriptive Latin: niger (black) and fasciatus (banded), referring to the dark horizontal markings along its flanks.
Morphology
Danio nigrofasciatus is one of the smallest members of its genus, with a maximum recorded standard length of approximately 1.5 in. Its body plan is the classic danio form: elongate, laterally compressed, with a slightly upturned mouth suited to surface and mid-water feeding, and the short barbels typical of the genus.
The common name dwarf spotted danio points to the distinctive dark spots or short dashes arranged in a horizontal series along the midline of each flank, giving a spotted-to-banded impression depending on the angle and light. The flanks carry a bluish or silvery ground colour overlaid with these dark markings, and the fins are largely translucent. Sexual dimorphism is modest: females are typically deeper-bellied and more rounded when gravid, while males remain slimmer and more torpedo-shaped.
Habitat
The native range of Danio nigrofasciatus is centred on the Myitkyina region of northern Myanmar, making it a geographically restricted species by danio standards. Its type locality places it firmly in the rivers and streams draining this highland-to-lowland transition zone of the upper Irrawaddy system.
FishBase records it as a tropical freshwater species of rivers, with spawning associated with plants and submerged roots — consistent with the typical danio preference for clear to moderately turbid, well-oxygenated flowing or still waters with riparian vegetation. Water chemistry parameters drawn from its habitat align with soft to moderately hard conditions (5–12 dGH) and slightly acidic to neutral pH (6.5–7.0), with temperatures in the tropical band of 75–82 °F. The habitat character — northern Myanmar hill and lowland streams — is broadly similar to the cooler, cleaner environments occupied by other upland danios.
Feeding
Like the rest of the genus, Danio nigrofasciatus is a generalist omnivore and opportunistic micropredator in the wild. Its upturned mouth and active swimming style suit a fish that takes small invertebrates, aquatic insect larvae, microcrustaceans and organic detritus from the surface and water column.
In captivity it accepts standard aquarium foods without difficulty: high-quality micro-pellets and fine flake food form the dietary staple, while small live and frozen items — daphnia, baby brine shrimp, micro-worm and finely chopped bloodworm — improve condition, enhance coloration and encourage natural feeding behaviour. Its small mouth size dictates appropriately sized food particles; items pitched for larger danios may be ignored or rejected.
Mating
Danio nigrofasciatus is an egg-scattering, non-guarding spawner in the typical danio mould. There is no nest construction, no pair bond beyond the act of spawning, and no parental investment in eggs or larvae. A conditioned male pursues a gravid female energetically through the water column and among vegetation, the pair releasing eggs and milt together in brief, side-by-side presses.
Spawning is promoted by the conditions that signal the seasonal rains in northern Myanmar — warmth, fresh clean water and access to fine-leaved plants or submerged roots where the eggs can settle out of the adults' reach. In a community tank without separation, adults will locate and consume eggs quickly, so reproductive success in captivity depends on providing cover or removing the adults promptly after spawning.
Breeding
Breeding Danio nigrofasciatus follows the standard protocol for small danios. A separate, shallow spawning tank fitted with a fine mesh or layer of glass marbles on the bottom — or a thick mat of fine-leaved plants such as java moss — allows the scattered, adhesive eggs to fall into gaps beyond the adults' reach. A small rise in temperature, a water change with slightly cooler fresh water, and the introduction of well-conditioned fish typically prompt spawning at first light.
Females may deposit a relatively small clutch given their diminutive size. Eggs should be left undisturbed after the adults are removed; they hatch in two to three days at 79 °F and the larvae become free-swimming within a few further days. First foods are the finest available: infusoria, commercial fry foods and newly hatched brine shrimp nauplii. Growth is relatively rapid and the young fish develop their characteristic dark flank markings within the first few weeks.
In the aquarium
Danio nigrofasciatus is a peaceful, active micro-danio suited to smaller aquaria of 10 US gal or more with like-sized, non-boisterous tankmates. As a strongly social species it must be kept in groups; a shoal of at least six to eight individuals is recommended to maintain natural behaviour and reduce stress. Kept in smaller numbers it may become shy or restless.
Water parameters should reflect the species' northern Myanmar origins: temperature 75–81 °F, pH 6.4–7.4, and soft to moderately hard water with attentive maintenance. Aqua-fish.net notes it as sensitive to water quality, making regular small water changes essential. Gentle filtration providing good oxygenation without strong turbulence suits it well. The tank should include fine-leaved planting and open swimming space; a darker substrate and subdued lighting tend to bring out the species' markings and encourage bolder behaviour. It is infrequently available in the trade and is best sourced from specialist cyprinid breeders.
Conservation
Danio nigrofasciatus is listed as Data Deficient (DD) on the IUCN Red List, assessed in March 2011. The DD designation reflects a genuine lack of field survey data rather than confirmed population health; the species' restricted range in northern Myanmar means that population-level information remains sparse and any quantification of trends is currently impossible.
Northern Myanmar has experienced significant land-use change, forest loss and agricultural expansion in recent decades, pressures that affect stream habitats throughout the Irrawaddy catchment. Given the species' apparently narrow native range and its dependence on clean, well-oxygenated river and stream habitats, it is plausible that localised threats exist — but without targeted surveys, no assessment of range, population size or trend is possible. Its small size and limited trade presence mean collection pressure is likely low, though habitat degradation remains the primary long-term concern across the region.