Emerald dwarf rasbora
Danio erythromicron
intermediate careOverview
The emerald dwarf rasbora (Danio erythromicron) is a beautifully marked nano fish from Inle Lake in Myanmar — under 2.5 cm, patterned with vertical emerald-and-copper bars and a flash of orange in the fins. A close relative of the celestial pearl danio, it is peaceful and shy, and unusually among prized nano fish it prefers harder, alkaline water, which makes it a gift for keepers whose tap water suits it.
Tank & water
A shoal thrives in a mature, planted 38-litre (10-gallon) tank or larger.
- Temperature: 20–25 °C from a small heater; it likes the cooler end of tropical, matching its highland lake home.
- Water: neutral to slightly hard and alkaline, pH 7.0–8.0 — no need to soften your water. Test with a kit.
- Densely planted: fine-leaved plants and some open swimming space give cover and confidence.
- Gentle flow: a soft sponge filter keeps the water clean without a strong current.
Feeding
Emerald dwarf rasboras are small-mouthed micropredators and omnivores. Offer fine crushed micro-pellets and powdered foods, supplemented with small live and frozen fare — baby brine shrimp, daphnia, cyclops and microworm. Feed little and often, and size everything down for their tiny mouths.
Behaviour & tankmates
Peaceful and slightly timid, they suit a calm nano community. Good tankmates are other small, gentle fish and dwarf shrimp — celestial pearl danios, small rasboras, pygmy corydoras and cherry shrimp. Avoid boisterous or fin-nipping fish. Keep them in a good shoal so their gentle sparring and displays play out naturally.
A well-fed shoal will often spawn among fine-leaved plants and moss in a mature tank, scattering eggs that the adults may eat, so a densely planted layout gives fry the best chance of surviving unaided. This makes the species a rewarding long-term project as well as an attractive display fish.
Give the emerald dwarf rasbora a planted, cooler, neutral-to-hard tank and a full shoal, and its striped, orange-flushed pattern makes it one of the most distinctive nano fish you can keep — see our best nano aquarium picks and best fish for a planted tank.
Emerald dwarf rasbora — frequently asked questions
Does the emerald dwarf rasbora want soft or hard water?
Unusually for a nano fish, it prefers neutral to slightly hard, alkaline water. It comes from Inle Lake in Myanmar, which is hard and alkaline, so it is a great choice for keepers with harder tap water — the opposite of soft blackwater nanos like the chili rasbora.
Is it a danio or a rasbora?
Scientifically it is a danio (Danio erythromicron), formerly placed in Microrasbora and Celestichthys, and it is a close relative of the celestial pearl danio. 'Emerald dwarf rasbora' is just the long-standing trade name; either way it is cared for as a small, shy, shoaling nano fish.
How many emerald dwarf rasboras should I keep?
Keep at least eight to ten. They are shy shoalers that colour up and behave naturally only in a decent group. Males display and spar gently among themselves in a shoal, which spreads any minor aggression and shows off their emerald bars and orange fins.
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