Emerald Dwarf Rasbora

The emerald dwarf rasbora (Danio erythromicron, also classified as Celestichthys erythromicron and formerly Microrasbora erythromicron) is a tiny, strikingly coloured cyprinid endemic to Lake Inle in Myanmar. Reaching a maximum size of only about 2 cm (0.8 in), 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, the water must be alkaline and moderately hard — pH 7.0–8.0 and hardness 12–25 dGH — matching the limestone geology of Lake Inle. They will not do well in soft, acidic conditions. 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 are micropredators that feed on small invertebrates and zooplankton; 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).