Taxonomy & naming
Danio dangila was described by Francis Hamilton in 1822 from the District of Munger, Bihar State, India — though the type specimens have since been lost. Hamilton originally placed it in the genus Cyprinus (then a catch-all for many cyprinids), and the Catalog of Fishes (Eschmeyer, the authority for valid names) records the current valid combination as Danio dangila (Hamilton, 1822), the parenthetical authority marking Hamilton's name's removal from its original genus.
The species accumulated several synonyms across the nineteenth and early twentieth centuries: Danio deyi, Perilampus reticulatus, and the more recent Danio meghalayensis have all been placed in synonymy with dangila. These synonymies reflect the confused early taxonomy of South Asian cyprinids, where wide-ranging, variable species were described multiple times from different parts of their range.
Within Danio, dangila belongs to the core group of 'true danios' — horizontally patterned, elongate schooling fishes of South and Southeast Asia. It is the largest recognised member of the genus. The common name 'moustached danio' alludes to the prominent pair of long barbels at the corners of the upper jaw, which are conspicuous in adults.
Morphology
Danio dangila is the largest species in the genus, with Seriously Fish recording a size range of 2.5–5 in SL and FishBase citing up to 6 in (6 in) for the biggest individuals — substantially larger than any of the common aquarium danios. The body is elongate, moderately compressed laterally, with a large, slightly oblique mouth bearing two pairs of barbels, the rostral pair short and the maxillary pair noticeably long and prominent, giving rise to the 'moustached' common name.
The flanks display a reticulate (net-like) pattern of dark-edged scales over a silvery to gold background, crossed by indistinct longitudinal lines; the pattern is more vivid in well-conditioned fish. The dorsal, anal, and caudal fins show traces of pigmentation, and a faint blue-green iridescence can be seen along the lower flank in good light. Mature females are noticeably deeper-bellied than males and broader across the body when carrying eggs.
Habitat
Across its extensive range in the Ganga-Brahmaputra drainage — spanning Nepal, Bhutan tributaries, northern and northeastern India, Bangladesh, and Myanmar — Danio dangila occupies a remarkably broad spectrum of freshwater habitats. Seriously Fish describes it as occurring from fast, clear mountain streams with rocky and stony riverbeds at higher elevations down to sluggish, swampy lowland environments with dense marginal and emergent vegetation.
This ecological flexibility sets it apart from many danios that are strongly tied to particular stream types. FishBase records it from clear, fast-flowing highland reaches with neutral to slightly acidic soft water, while lowland records come from warmer, more turbid conditions. A regional study from the northeastern hill region of India confirms the species' presence across varied microhabitats within a single drainage.
SeriouslyFish gives water parameters of 61–75 °F, pH 6.5–7.5, and hardness of 36–268 ppm — an exceptionally wide hardness tolerance consistent with a species that bridges soft hill streams and harder, more productive lowland waters.
Feeding
In the wild, Danio dangila is an opportunistic omnivore. Seriously Fish notes that its natural diet consists primarily of insects and their aquatic larvae taken from and near the surface, in keeping with the upturned-to-oblique mouth typical of danios that feed in the upper water column. Plant matter, small invertebrates, and organic detritus likely supplement the diet depending on season and habitat.
In captivity it proves undemanding: good-quality dried foods — flakes and pellets of appropriate size — are accepted readily, and condition and colour are maintained best when the diet is supplemented regularly with live or frozen foods such as bloodworms, daphnia, and brine shrimp. Given its size, it can handle larger food items than its smaller relatives, and it feeds assertively in a group.
Mating
Like all members of the genus, Danio dangila is an egg-scattering, non-guarding spawner. Spawning is triggered by warm, clean water and seasonal cues, with fish in their natural range breeding in response to monsoon flooding and rising temperatures. Courtship is energetic: males pursue ripe females through vegetation and open water, pressing alongside them as eggs and milt are released simultaneously.
There is no pair bond and no territorial behaviour surrounding the act of spawning. Eggs are scattered over fine-leaved plants, moss, sandy substrate, or gravel and receive no further attention from either parent. Adults will consume eggs given the opportunity, which is why separation of adults from the spawn is standard practice in captive breeding.
Breeding
Danio dangila is an egg-scatterer that spawns in groups, following the typical danio pattern described by Seriously Fish. Captive breeding follows the standard procedure for larger egg-scattering cyprinids: a spacious, shallow spawning tank with clumps of fine-leaved plants or a mesh covering the bottom is set up to protect eggs from being eaten. A well-conditioned group — ideally more males than females — is introduced, and spawning typically occurs in the morning following a small temperature rise or water change.
Females may deposit several hundred eggs per session. The adults are removed promptly after spawning. Eggs hatch within two to three days at typical temperatures in the stated range; larvae become free-swimming after a further few days and accept small live foods (infusoria, then newly hatched brine shrimp) before graduating to finely crushed dry foods. Growth is moderately rapid for a fish of this size, and juveniles are best grown on in a roomy, well-filtered tank.
In the aquarium
Because Danio dangila reaches 5 in or more, it requires substantially more space than the common aquarium danios — a tank of at least 59 in in length is appropriate for a proper shoal of six or more adults. It is an active, mid-to-upper water swimmer that appreciates open swimming corridors, gentle to moderate current, and patches of planting around the perimeter. Being a cool-tolerant species with a preferred range of 61–75 °F, it does not need a heater in a warm temperate room and should not be kept alongside fish that require consistently high tropical temperatures.
Water quality should be good and well-oxygenated, reflecting its natural association with clear streams; softer, slightly acidic to neutral water (pH 6.5–7.5) is ideal, though the species' wide hardness tolerance means it adapts to harder tap water without difficulty. Suitable tankmates are other robust, active fishes of similar size; its bold, shoaling nature makes it too energetic for delicate or slow-moving companions. It is an undemanding and rewarding fish for the hobbyist who can provide the required space.
Conservation
Danio dangila is assessed as Least Concern (LC) on the IUCN Red List, assessed in 2010. The assessment notes a wide distribution across the Ganga-Brahmaputra system with stable or increasing populations in many parts of its range, attributed to widespread habitat availability. Its ecological breadth — spanning fast highland streams and slow lowland swamps — buffers it against the loss of any single habitat type.
The species also features in the ornamental fish trade, with a regional study from northeastern India confirming its collection and availability for the aquarium hobby. Most pressure in that study derived from local collection rather than industrial harvest, and the wide natural range means localised extraction is unlikely to threaten the species overall. Broader pressures on freshwater biodiversity in the Ganga-Brahmaputra drainage — agricultural runoff, sedimentation, and wetland modification — remain background concerns applicable across the basin, but none currently threaten this adaptable and widespread cyprinid.