Emerald Dwarf Rasbora

Scientific name: Celestichthys erythromicron, also listed as Danio erythromicron

Adult size: about 2 cm

Origin: Lake Inle, Shan State, Myanmar

Water: 20–24 °C, pH 7.0–8.0, 12–20 dGH

Group: 10 or more, ideally 20

Diet: tiny live, frozen and dried foods

Temperament: timid, peaceful toward other species

The emerald dwarf rasbora is a small barred fish of about 2 cm, with fine dark vertical bars over a gold-green body, a dark spot at the base of the tail and, on mature males, orange-red fins. It is not a true rasbora but a close relative of the celestial pearl danio, and both are now placed in Celestichthys. It is known only from Lake Inle, an isolated mountain lake in Shan State, eastern Myanmar, and its surrounding watershed, where the water is clear, hard and alkaline and grows thick beds of aquatic plants. That origin matters: unlike most nano fish it prefers hard, alkaline water and cooler temperatures. It is less frantic than a danio and spends its time picking at plant surfaces, so it shows best in a planted tank. It is timid and shoals loosely; Seriously Fish suggests buying as many as possible, ideally 20 or more. Dominant males can be combative with each other but rarely bother other species.

Water: 20–24 °C and pH 7.0–8.0, hardness 12–20 dGH, so cool, hard and alkaline. GH measures dissolved calcium and magnesium; this is one of the few nano fish that wants a high reading. Keep it stable with regular partial water changes.

Tank and planting: densely planted with fine-leaved plants and mosses, gentle flow and moderate light. Plenty of cover lets the timid fish come out.

Feeding: small live and frozen foods such as daphnia, cyclops and baby brine shrimp, with fine dried food as a supplement but not the whole diet.