Cyprinids (Cyprinidae)

Dwarf Danio

Microdevario nanus

Microdevario nanus, known as the Green Dwarf Danio, belongs to the family Cyprinidae. Until 2009, this fish was classified as a Rasbora, being called the Green Dwarf Rasbora. However, further research moved the species into the genus Microdevario, which is closely related to the danios. Despite this, both names remain in active use and are considered interchangeable in common parlance.

Tank
from 40 L (11 gal)
Temperature
20 – 27 °C (68 – 81 °F)
Size in aquarium
1.5 – 2 cm (0.6 – 0.8 in)
Acidity
pH 6–7.5
Natural rangeRange on the map
  • Ayeyarwady Delta area
  • Myanmar

Tank conditions

Plan the tank stocking
Temperature
20 – 27 °C (68 – 81 °F)
Water pH
Slightly acidic (6) – Neutral (7.5)
Water dH
Very soft (3) – Hard (13)
Water salinity
no salt (freshwater)
Size in aquarium
1.5 – 2 cm (0.6 – 0.8 in)
Lifespan
3 years
Temperament
Peaceful, active/mobile
Toward small fish
not a predator
Required aquarium volume
from 40 L (11 gal)
Lighting
dimmed or moderate
Substrate
fine sand
Water flow
weak
Feeding
Mixed diet meat + plant-based
Keeping
Schooling usually from 5–6 individuals and more
  • Lifespan. A lifespan to expect under good care, not a measured value: it depends heavily on tank volume, water quality and diet — and for selectively bred forms, on their origin as well.
  • Toward small fish. Based on the Predators category in the catalog or the temperament in the species parameters. “A risk to small fish” means the species is not a predator by habit, yet will swallow any fish that fits in its mouth.
  • Required aquarium volume. This is a husbandry recommendation, not a measured value: the volume depends on the keeping mode (schooling (usually from 5–6 individuals and more)), footprint, decor and tank mates.

Care and keeping

Description

Outwardly, the Green Dwarf Danio resembles its close relatives, such as Danio kyathit and Microdevario kubotai, but differs from them in its smaller size, reaching only about 1.5 cm. Another characteristic feature is a dark spot on the dorsal fin. The fish's coloration is predominantly silvery with greenish iridescence. Sexual dimorphism in this species is not pronounced, making it quite difficult to distinguish males from females.

Habitat

This species originates from Southeast Asia, specifically from the southern regions of Myanmar (Burma), where it can be found primarily in the Irrawaddy River delta. Its natural habitats are characterized by abundant vegetation and murky water containing a significant amount of silt, as well as many overgrown channels and swampy areas. As a result of human economic activity, rice fields have appeared in vast areas of the region, which have become a new habitat for the Green Dwarf Danio.

Behavior and Compatibility

These peaceful, schooling fish feel comfortable in groups of at least 8–10 individuals. They coexist well with other species of comparable size. However, proximity to larger fish should be avoided, as they pose a potential danger to the Green Dwarf Danio.

Care and Maintenance

An aquarium of 40 L or more is suitable for these miniature creatures. The setup should include plenty of aquatic plants, both rooted and floating. Floating plants will provide the necessary shading, which will help to more effectively bring out the emerald hues of the Green Dwarf Danio. Lighting should be subdued. Since the fish tolerate neither strong nor moderate currents well, it is important to carefully choose a filter, which is the main source of water movement in the aquarium. If the number of inhabitants is small, an airlift filter with a sponge as a filter element may be an optimal choice. It provides gentle water movement, effectively cleans it, and saturates it with oxygen. However, its low performance and insufficient effectiveness for aquariums with many large fish should be considered. With a significant number of live plants, additional aerator diffusers may be required to prevent oxygen starvation at night. This is because photosynthesis stops at night, and plants begin to actively release carbon dioxide absorbed during the day. Aquarium maintenance includes standard procedures: weekly partial water changes, removal of organic debris and buildup, equipment prophylaxis, and regular monitoring and maintenance of stable pH and dGH values.

Diet

These fish readily accept all popular foods intended for aquarium inhabitants of appropriate size. Their daily diet can consist of dry flakes or granules, supplemented with live or frozen foods such as Artemia, Daphnia, or finely chopped bloodworms.

Breeding and Reproduction

At the time of writing this article, there is no reliable data on the successful breeding of this species in home aquariums. Nevertheless, given its close relationship to Microdevario kubotai, it can be assumed that their breeding characteristics may be similar. Under favorable conditions, spawning can occur regularly throughout the year. The fish scatter their eggs among dense vegetation, showing no parental care and may eat their own eggs. Although fry may appear in the main aquarium, their survival to adulthood will be extremely low if they are not transferred to a separate tank.

Diseases

In a balanced aquarium ecosystem that meets the needs of this species, diseases are rare. Most often, ailments are provoked by deteriorating environmental conditions, contact with already sick fish, or mechanical damage. If the fish shows clear signs of illness, medicinal treatment should be applied.

How to choose

When purchasing, choose active individuals that stay in the water column and show no signs of sluggishness or apathy. It is important to carefully inspect the fish for damage to scales, fins, and the absence of white film or ulcers on the body. Since this species is very small, it is worth ensuring that the store does not have emaciated specimens, as recovery after prolonged starvation is extremely difficult for fry and miniature fish. — avoid fish with sunken bellies or abnormally bloated abdomens — prefer individuals with clean, transparent fins without signs of rot — purchase a group of 8–10 individuals at once, as single fish in a store are often under severe stress.

Compatibility

There are no pair reviews for this species yet — check tankmates in the matcher.

All tankmates

Plants and this fish

Matching water does not mean the plant will stay intact.

Frequently asked questions

The essentials: size, tank volume, water parameters and care

How big does Dwarf Danio get?

An adult reaches 1.5–2 cm in length. Plan the tank around the maximum size: the fish quickly outgrows a cramped setup.

What size aquarium does Dwarf Danio need?

The recommended volume is 40 L. A smaller tank speeds up nitrate build-up and raises stress levels.

What water parameters does Dwarf Danio need?

Temperature 20–27 °C, pH 6–7.5, hardness 3–13 dGH. Stability matters more than exact values: sudden swings are harder on the fish than a small deviation from the ideal.

How long does Dwarf Danio live?

Around 3 years when kept properly. Lifespan depends directly on tank volume, water quality and a varied diet.

Is Dwarf Danio aggressive?

Temperament: peaceful, active/mobile. Keep this in mind when choosing tank mates.

How many Dwarf Danio should be kept together?

Recommended setup: schooling (usually from 5–6 individuals and more). Ignoring this is a common cause of stress and disease.

What does Dwarf Danio eat?

Diet type: mixed diet (meat + plant-based). Feed small portions that are finished within a couple of minutes — overfeeding does more harm than underfeeding.

What is the scientific name of Dwarf Danio?

The scientific name of the species is Microdevario nanus, family Cyprinids (Cyprinidae). It also appears in the literature as: Microrasbora nana.

Similar fishes

Matched by family, categories and overlapping keeping conditions

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Other scientific names and conservation status

Other scientific names
Microrasbora nana