Emerald dwarf rasbora

Danio erythromicron

A micro-fish endemic to Lake Inlé in Myanmar, with vertical emerald green and orange bands on a translucent body — a tiny jewel reaching just 2 cm. Despite its common name containing 'rasbora', it is scientifically a Danio. Requires alkaline, hard water (pH 7.0–8.0), an exception compared to many tropical nano fish. In groups of 8–10+ in densely planted tanks with dim lighting, males display competitive behaviors that enhance coloration. Males may spar in groups that are too small.

Family: Danionidae
Origin: Myanmar
Origin: Extra-Amazon South AmericaNorth AmericaSouth and Southeast Asia
Tank use: Used in 0 tanks

Species challenges

Temperature

20 °C - 24 °C

7 - 8

Water type

Freshwater

Tank level

Middle

Adult size

2.5 cm

Description

Geographic Origin and Biotope: Endemic to Lake Inle in Myanmar. Lives in calm and crystalline waters surrounded by limestone mountains, hiding among the dense expanses of floating islands of vegetation.

Taxonomy and Morphology: Emerald Dwarf Rasbora (Danio erythromicron, formerly Microrasbora). Miniature cyprinid, totally lacks barbels (a rare feature for Danios) and has a compact and stocky body shape.

Social Behavior: Extremely shy and reserved. Must be kept in colonies of 15-20 specimens; in smaller numbers it will hide perpetually. Males engage in ritual dances with flared fins, creating temporary micro-territories.

Coloration and Sexual Dimorphism: Stunning: emerald green or iridescent coppery body, banded by 12-15 thin vertical dark blue/black stripes. Black spot at the base of the tail, orange fins. Females are more faded, silvery and with a round belly.

Care and observations

Aquarium Setup: Nano-aquariums (minimum 60 cm / 24 inches) densely, if not obsessively, planted. Use dark bottoms, floaters and mosses (Taxiphyllum) to shield the light and instill security. Practically still water (no strong currents).

Diet and Feeding: Micro-predator. Hardly comes to the surface. Must be fed in the water column with very small live or frozen food (brine shrimp nauplii, microworms, cyclops, daphnia). Crumbled dry food is accepted with difficulty.

Water Quality: Limestone upland fish. Tolerates pH up to 8.0 and very hard waters well. On the other hand, it suffers from excessively acidic and soft water, or tropical tanks kept stably over 26°C (79°F).

Compatibility and Tankmates: Not suitable for typical community aquariums, it would be bullied or its food ignored. Pair it only with other nano species (Boraras, Danio margaritatus) and small Caridina or Neocaridina shrimp.

Aquarium Reproduction: They lay a very few slightly adhesive eggs daily among the moss. By regularly removing the moss to place it in separate small tanks, fry will be obtained, to be fed with infusoria.

Risks and Diseases: Rapid wasting if placed in bare or brightly lit tanks. Easy prey to skin parasites if stressed by the presence of large fish.

Fish profile

Temperament: Pacifico e timido; i maschi competono con display cromatici. Tenere in gruppi di almeno 8–10
Diet: Onnivoro micro-predatore: fiocchi fini, micro-pellet, nauplii di artemia, dafnia, micro-vermi vivi o surgelati
Tank level: Middle
Minimum group: 8
Adult size: 2.5 cm
Minimum tank: 40 L
GH: 10 dGH - 20 dGH
KH: n/a
TDS: n/a
Conductivity: n/a
Feeding frequency: 2 volte al giorno
Bioload: Negligible
Flow: Corrente debole
Reproduction: Oviparo a dispersione senza cure parentali. Depositore entusiasta in condizioni ottimali. Vasca dedicata con muschio di Giava o mop. Rimuovere i genitori: predano le uova. Avannotti: infusori, poi nauplii di artemia.
Compatibility: Solo con nano-pesci pacifici: Celestial Pearl Danio, Corydoras pygmaeus, gamberetti Neocaridina. Evitare pesci grandi o turbolenti.

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.