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Emerald Dwarf Danio – Celestichthys eryrthromicron


Emerald Dwarf Danio

Danios are amongst the most popular aquarium fishes. There are probably more than 30 distinct species of Danio from which the aquarist may choose and this includes a large number of visually stunning fishes that are bound to enhance any home aquarium.

Is the Emerald Dwarf Danio a good community fish? The Emerald Dwarf Danio should be considered to be an excellent community fish assuming that the community is one of smaller species, being that adults are less than one-inch long. The Emerald Dwarf Danio is suitable for novice aquarists as it gets on just fine with other similar-sized species. 

Key Facts

CategoryKey Facts
Common name(s)Emerald Dwarf Danio – also knows as:
Emerald Dwarf Rasbora
Thick-band Purple Zebra Danios
Cross-banded Dwarf Rasboras
Scientific nameCelestichthys eryrthromicron
FamilyCyprinidae
Originate fromLake of Inlé and surrounding watershed in Shan state, eastern Myanmar, and also occurs close to Loi Kaw township in neighboring Kayah state to the south in south Asia
Care requiredEasy to care for and hugely popular
TemperamentPlacid, timid shoaling fish
Colour & FormCarp-shaped with almost clear finnage and iridesccent turquoise, vertical markings along its flanks and black spot on caudal peduncle.
LifespanUp to 5 years
Adult sizeLess than 1 inch
DietOmnivorous – eat aquatic insect larvae in nature
Aquarium size24 inches in length or greater
Compatible withMost other Tetras, Barbs, Danios, Guppies and other livebearers, dwarf cichlids, smaller Gouramis, catfish and loaches that live in fairly neutral, soft water
Avoid keeping withLarge and/or aggressive species
BreedingEasy if you put the fish in the right environment.
Water temp70 – 75 Fahrenheit
Water pH7.0 to 8.0
Water hardness (dGH or dH)1 to 10 dGH

Origins of the Emerald Dwarf Danio

Danios, as a “family” of fishes belonging to the biological family Cyprinidae and are found in nature in south and southeast Asia.

The Emerald Dwarf Danio originates from the isolated mountain lake of Inlé and surrounding watershed in Shan state, eastern Myanmar, and also occurs close to Loi Kaw township in neighboring Kayah state to the south in south Asia.

Characteristics of the Emerald Dwarf Danio

As you can see, the Emerald Dwarf Danio is an impressive little fish. It has a carp-shaped body, and It will grow to up to almost 1 inch in the aquarium and lives for up to five years.

Emerald Dwarf Danios prefer fairly soft, neutral water with a pH of 7.0 to 8.0 with a temperature range between 70 and 75 degrees Fahrenheit and up to 10 dGH. 

The Emerald Dwarf Danio enjoys soft to medium, neutral water conditions so it will be comfortable with other species of similar size that prefer this type of water chemistry.

The female is generally larger and hardier than the male but the male, as is often the cases amongst species of fish, is the more colorful of the pair.

A well-planted aquarium with open space in which the Emerald Dwarf Danio can swim freely is preferred together with a decent flow of water.

The Emerald Dwarf Danio is a shy fish, not always on the go, so it is best to avoid putting it with hyperactive species, especially if the latter are significantly larger and/or aggressive.

The Emerald Dwarf Danio is a shoaling fish and should be kept as a group of at least six fish, though a shoal of, say, twenty or more fish is highly recommended. Since this is a small species, there is every reason to have a decent-sized shoal to ensure that it has plenty of scope in which to behave naturally, as it always does better in a larger shoal.

Having plenty of vegetation to break up lines of sight will also help to protect your Emerald Dwarf Danios from predation but it is obviously advised that Emerald Dwarf Danios are not kept with predatory species, as they are a very peaceful fish and may be seen as prey.

The body of the Emerald Dwarf Danio in good condition striking, often iridescent, turquoise, vertical stripes along its flanks. The male can become deeply colored during spawning. The pelvic and anal fins of the male also have a more orange hue than the female, as do the gill plates. There is usually a black spot to the rear of the caudal peduncle. The head area and backwards over the dorsal area is a pinkish gold in color, which matches the scales between the vertical, turquoise stripes along the flanks.

Overall, the fish is attractive and most elegant.

It is fairly to distinguish the sex of adult Emerald Dwarf Danios because the adult female is larger and less colorful. The female is also fuller-bodied, especially when carrying eggs (gravid). 

The Emerald Dwarf Danio tends to inhabit the middle and lower areas of the aquarium. That said, it is a vigorous fish when breeding and will readily traverse the entire aquarium. It tends to feed in the middle and lower areas of its environment and, being quite a tiny fish will prefer small (preferably live) food. They love brine shrimp, blood worms, tubifex worms and daphnia at least a couple of times each week but will accept freeze-dried food as well as flake food.

The Emerald Dwarf Danio is, by nature, a shoaling fish and it is generally recommended to purchase at least six fish – preferably twelve to twenty-four fish, as their nature is to swim together like a shoal and they will tend to thrive much better as a shoal. Emerald Dwarf Danios are excellent, tiny community fish and are ideal for novice aquarists assuming that the soft, neutral water and appropriate breeding conditions required are provided and maintained.

It is generally advised that the minimum tank size for Emerald Dwarf Danios should be one of at least 24 inches in length or more due to the shoaling nature of the species and the fact that they are very active swimmers indeed, which will enable a small shoal to move around freely. A smaller tank might be too restrictive and the fish will suffer as a result.

There is a predominance of so-called “Nano tanks” available but, being old-fashioned, I prefer my fishes live in an environment which, at least, attempts to mimic nature, rather than living in what I would liken to a prison cell. The tank should be well-planted but with clear areas where the fish can swim freely. The water should have a gentle movement, as Danios enjoy swimming against a gentle flow of water.

Emerald Dwarf Danios are difficult to sex until they are mature, where the female has a slightly fuller body when she is carrying eggs (gravid) than the male, which is likely to take on richer coloring. 

The general rule for Danios is that by keeping six or more of the same species in an aquarium they will be fully aware of which is male and which is female and they will act accordingly when the time comes for breeding.

Emerald Dwarf Danio – Videos

How do Emerald Dwarf Danios breed?

Danios, in general, will scatter eggs by laying them over fine plants such as Cabomba, Fontanalis or Willow Moss or Java Moss.

Emerald Dwarf Danios are like most other Danios in that they scatter their eggs. In respect of preparing a breeding tank for the Emerald Dwarf Danio, it is generally recommended that the bottom is covered in marbles between which the eggs will naturally fall, safe from predation from its parents.

As the female Emerald Dwarf Danio becomes ripe with eggs, the difference between the sexes may become more evident, as the body expands because it is carrying eggs. If you plan to attempt to breed Emerald Dwarf Danios then it is recommended that you have a breeding tank prepared. Such a tank can be empty and should be tall and not more than filled to around nine-inches deep with water.

The water should have a reasonable current so the pump should not only be able to draw sufficient water to pump back as a current but should also include protection to ensure that the eggs do not get pulled through the pump.

The breeding pair will go through their mating ritual and the female release some of her eggs and the male will fertilize them until up to 30 eggs, perhaps more, have been laid and fertilized.

Thereafter, the adults will take no further part in rearing their offspring and will eat the eggs, given the chance so it’s best to return them to the main tank.

It takes around forty-eight hours for the eggs to hatch, depending on the water conditions and temperature and around a further seventy-two hours or so for the yolk sacs to be depleted and the fry to become free-swimming.

In a well-planted aquarium, the Emerald Dwarf Danio will often spawn in the community tank and at least some of the fittest fry will survive to adulthood.

Breeding tank for Emerald Dwarf Danios

You should prepare a tank of around five gallons in size with mature, soft, neutral water. The water should have a low level of light and be no more than around six-inches deep. It is recommended that the substrate consists of marbles through which the fry will fall.

By all means, include plants such as Java Moss or, perhaps, a sterile spawning mop to encourage breeding but take into account the fact that you will need to remove the adults once spawning is completed and you don’t want to injure either the fishes or the eggs.

Danios prefer to spawn where the water is flowing do a decent pump is required to synthesize that flow and the marbles will help to prevent the eggs from being drawn into the pump or consumed by the parents.

You may wish to introduce baby brine shrimp, mosquito larvae or bloodworm as an inducement to reproduction.

The male and female will swim amongst the plants (if any) and the female will lay laying around 30 eggs during a spawning. The male(s) will swim alongside or behind her and fertilize the eggs as they are laid. The eggs are not adhesive and will fall to the bottom of the tank. Once the female has laid all her eggs the adults should be removed from the breeding tank.

Reduce the water movement by turning down the pump – only regular aeration is now required. Keep the lights off (or very low) and the tank dark (of fairly dark)  because eggs and fry can be particularly sensitive to the light.

The eggs will hatch typically in a day or two depending on tank temperature and conditions and the fry will become free-swimming after around two days after hatching. Keep the tank unlit for the first week or so then gradually increase the lighting. Bear in mind that the eggs and fry of a fish as small as the Emerald Dwarf Danio will be tiny indeed so you may need to use a magnifier “app” on your smartphone to see anything at all.

The newly hatched fry will feed firstly on their yolk sac but, once free-swimming, can be fed infusoria (particularly rotifers) and will also thrive on egg yolk during the first two to four weeks. It is worth mentioning that immediately after hatching, fry seem quite vigorous but will soon go into a resting state before they become free-swimming so please don’t mistake this initial stage as being free-swimming.

Once the fry are free-swimming and their yolk sacs are depleted, then add baby brine shrimp. Once the fry are sufficient in size not to be treated as a snack then they can be introduced into the community tank where they will join the existing shoal. Before moving the adolescent fish into the community tank ensure that you have balanced the water temperatures to mitigate the risk of White Spot or other diseases being triggered.

Unless you are breeding commercially, you may wish to consider moving the fry into the community tank sooner rather than later. It may seem harsh but the adult fish in the tank will deal with any fry that are unlikely to survive to adulthood in the wild and you are synthesizing, to the best of your ability, a wild environment. The fittest fry will probably survive whilst the rest will be dealt with by the community.

Should your Emerald Dwarf Danios have a special diet for breeding?

Adult Emerald Dwarf Danios don’t need any particular inducement to breed. That said, it has been suggested that adding baby brine shrimp, mosquito larva may encourage them, presumably because the addition of a new food may “fool” the fish into thinking that it is breeding time. From my own experience, I would always recommend keeping all of your fish in the best possible condition at all times, as this is good for the wellbeing of your fish.

Mike Wheeler

I started keeping freshwater tropical fish in 1972 and it has been something of a passion ever since. In this website, my aim is to build up an everyman's guide to help the everyday aquarist get the best from this inspiring and entertaining hobby.

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