Taxonomy & naming
Danio tinwini was formally described by Sven O. Kullander and Fang Fang in 2009 in the journal Ichthyological Exploration of Freshwaters (volume 20, number 3, pages 223–228). The holotype, NRM 60337, is a male measuring 1 in standard length, collected from the stream near Shatrazyut village on the road from Mogaung to Tanai, Kachin State, Myanmar, at approximately 25°54'54"N 96°39'48"E — a tributary within the Ayeyarwaddy drainage.
The species sits within the genus Danio as recognised by the Catalog of Fishes (Eschmeyer, the authority for valid names). Some older literature and hobbyist sources list it under Brachydanio, a genus name that has been applied to the smaller danios at various times; we follow the current Catalog of Fishes in treating Brachydanio as a synonym of Danio. GBIF maps the species under its current valid combination Danio tinwini Kullander & Fang, 2009.
The specific epithet honours U Tin Win, a Burmese fish collector and exporter instrumental in bringing Myanmar's cyprinid fauna to the attention of ichthyologists and the aquarium trade.
Morphology
The gold ring danio is one of the smallest danios known: males reach approximately 1 in standard length, and females are marginally larger at around 1 in SL. The body is slender and laterally compressed in the typical danio fashion, with a slightly upturned mouth carrying shorter barbels than those of closely related species — a useful distinguishing character.
The most striking feature is the spotted patterning of the unpaired fins. Rather than the clean horizontal stripes of the zebra danio or the solid spots of some congeners, D. tinwini displays rings or dark-edged spots with golden centres arranged in rows across the dorsal, caudal and anal fins — the trait that gives it the common name gold ring danio. Body coloration is pale silver-gold with faint barring or spotting. The species is accomplished at jumping and will clear an uncovered tank with ease.
Habitat
Danio tinwini is endemic to Myanmar, known from the Mogaung Chaung stream in Myitkyina District, Kachin State, within the upper Ayeyarwaddy drainage of northern Myanmar. It inhabits slower-moving marginal sections of well-oxygenated streams — the quieter edges, side pools and backwaters adjacent to faster flow, typically in water that remains cool and clear.
Water parameters recorded from suitable habitats and reflected in husbandry data suggest soft to moderately hard water — broadly 18–90 ppm hardness — with a slightly acidic to neutral pH of 6.5–7.5 and temperatures between 18 and 79 °F. These conditions are consistent with the cool, seasonally variable hill streams of northern Myanmar at moderate elevation, distinct from the warmer, more acidic blackwaters of Sundaland to the south.
Feeding
Like all danios, D. tinwini is an omnivorous micropredator. In the wild it feeds on small invertebrates — aquatic and terrestrial insect larvae, microcrustaceans and similar prey — taken from the surface film and the water column. Its upturned mouth is adapted for intercepting items at and near the surface.
In the aquarium it accepts a broad range of appropriately sized foods: high-quality micro-pellets, small flake, and live or frozen invertebrates such as Daphnia, bloodworm (chironomid larvae) and Artemia nauplii. Given its very small size, food particle size matters — even standard flake may be too large for the smallest individuals, so crushed flake or purpose-made micro-foods are recommended. Varied feeding maintains colour and condition.
Mating
Danio tinwini is an egg-scattering, non-guarding spawner with no pair bond and no parental care, following the reproductive strategy shared by the great majority of danios. A driven male pursues a gravid female through the cover of fine-leaved plants or moss, pressing alongside her as eggs and milt are released simultaneously into the vegetation or substrate.
Spawning in the wild is likely tied to the seasonal hydrology of Kachin State's streams — rising water levels and cooling or warming temperature shifts associated with the monsoon may act as proximal triggers, as they do for many small Asian cyprinids. In captivity, conditioning with live and frozen foods, a slight temperature rise and the addition of fresh, slightly cooler water can stimulate spawning behaviour in a well-maintained group.
Breeding
To breed D. tinwini, a small, well-planted tank with fine-leaved plants, Java moss or a spawning mop over a bare or marbled base is effective. A conditioned group or a single pair is introduced; eggs are scattered and fall or lodge among the plants, where adults will actively consume them if given the opportunity. The breeding group is removed after spawning is observed.
Eggs are small and hatch in approximately two days at typical temperatures; larvae become free-swimming within a few days and are initially very small. First foods must be correspondingly fine: infusoria, paramecia or commercial ultra-fine fry foods, progressing to Artemia nauplii once the fry are large enough. The species gives no parental care whatsoever — both parents must be removed to protect the eggs. Rearing the fry to a saleable size requires patience and pristine water quality.
In the aquarium
The gold ring danio is best suited to a small planted aquarium of 10–15 US gal or more, kept as a school of at least eight to ten individuals. Like all danios it is a strong schooling fish that becomes notably less confident and may be harassed by larger tankmates when kept in small numbers; a proper school keeps the fish active, visible and relaxed. Its very small size — under 1 in — makes it an ideal candidate for a nano or species aquarium, and it mixes well with other small, peaceful fish of similar size and water requirements.
Water should be soft to moderately hard (18–90 ppm), slightly acidic to neutral (pH 6.5–7.5), and maintained at 64–79 °F — the lower end of this range is tolerable and helps replicate the cool streams of northern Myanmar. A tightly fitting lid is essential: this species is an accomplished jumper and will find any gap. Planted tanks with gentle flow suit it well; dense vegetation along the margins provides refuge, while open midwater gives the school space to move.
Conservation
Danio tinwini has not been formally assessed by the IUCN Red List and is considered Not Evaluated. The species is recently described (2009), Myanmar-endemic, and known from a geographically restricted area within the Ayeyarwaddy drainage of Kachin State — a combination of factors that would typically warrant at least a Data Deficient designation were an assessment to be conducted.
Kachin State has experienced significant land-use change including logging, agricultural expansion and infrastructure development that can alter stream hydrology and degrade the marginal, slow-moving habitat this species occupies. Its restricted known range and small body size make it potentially vulnerable to local habitat loss. The aquarium trade relies primarily on captive-bred stock, which reduces pressure on wild populations, but the status of wild populations in their native streams remains poorly documented and warrants dedicated survey work.