Emerald Dwarf Rasbora

The emerald dwarf rasbora (Danio erythromicron, also classified as Celestichthys erythromicron and formerly Microrasbora erythromicron) is a tiny, strikingly coloured cyprinid native to Lake Inle and its surrounding watershed in Myanmar. Reaching about 2 cm standard length, it features an iridescent emerald-green body with a series of vertical dark bars and vivid red highlights on the dorsal and caudal fins. Lake Inle is a shallow, high-altitude (∼900 m) limestone lake, and this species reflects those conditions in its care requirements.

Despite its minute size, the emerald dwarf rasbora needs a tank with a footprint of at least 60 × 30 cm (~54 L / 15 gal) due to the sometimes combative behaviour of dominant males. A densely planted setup with a dark substrate, floating plants, and gentle sponge filtration mirrors its natural habitat. Crucially, provide neutral to mildly alkaline, moderately hard water — pH 7.0–8.0 and hardness 12–20 dGH — matching the limestone geology of Lake Inle. Provide neutral-to-alkaline water. Temperature should be kept on the cool side at 20–24°C.

This species is timid and shoaling by nature, and is best kept in groups of 20 or more to spread intra-species aggression and encourage natural boldness. They probably feed on small invertebrates, algae and other small organisms in nature; offer daily meals of small live and frozen foods such as Daphnia and Artemia, alongside high-quality micro-pellets. They rarely rise to the surface, so sinking or slow-sinking foods are preferred. Suitable tankmates include other small Myanmar cyprinids such as Celestichthys choprae and Microdevario species. Avoid hybridisation risk with galaxy rasboras (Celestichthys margaritatus).

Keep twenty or more fish where space allows. Provide a base of at least 60 × 30 cm with dense cover.