Emerald dwarf rasbora

Danio erythromicron

Also known as Celestichthys erythromicron, Microrasbora erythromicron

FreshwaterFish

Emerald dwarf rasbora (Danio erythromicron) — Cantospira · CC BY-SA 4.0

Care at a glance

Temperature: 68–75°F (20–24°C)
pH: 7.0–7.8
Adult size: 0.8 in (2 cm)
Minimum tank: 11 gal (40 L)
Temperament: Peaceful
Social behavior: Schooling
Swim level: Middle
Difficulty: Medium
Breeding: Medium
Rarity: Common
Origin: Lake Inle basin, Shan State, Myanmar
Family: Cyprinidae

Overview

Keep them in a group of at least 8 to 10, and 20 or more brings out their best color and confidence while spreading out mild sparring between males. They are peaceful, timid middle-swimmers and loose shoalers rather than tight schoolers, so house them only with other small, calm species and no boisterous tankmates. Because they come from a cool, high-elevation lake, hold the temperature between 20 and 24 C and never let it climb above about 25 to 26 C, which makes them a poor fit for warm tropical communities. Do not keep them with the closely related celestial pearl danio, also called the galaxy rasbora, since the two can hybridize. They spawn readily in a mature planted tank, but adults eat the eggs, so a separate spawning setup raises the yield.

In the wild

Emerald dwarf rasboras are endemic to Lake Inle, a shallow high-elevation lake in Shan State, Myanmar. The lake sits on limestone, so the water is clear, neutral to slightly alkaline, and cooler than most tropical setups. Give them a tank of at least 40 liters with dense planting, a dark substrate, dim light, and gentle filtration from a sponge filter. Keep the pH between 7 and 7.8 and avoid driftwood or leaf litter, since tannin-stained acidic water does not suit them.

Good to know

This is a tiny cyprinid in the family Cyprinidae, reaching only about 2 cm as an adult. It has also been classified as Celestichthys erythromicron and Microrasbora erythromicron over the years. It is an egg scatterer with no parental care, and breeding is of medium difficulty.

Did you know

For such a small fish it is strongly tied to one place. Emerald dwarf rasboras live only in the Lake Inle basin, and their preference for cool, limestone-buffered water reflects that single high-elevation home rather than the warm soft-water streams most nano fish come from.