Fascinating and colorful, the Emerald Dwarf Rasbora, also known as Danio Erythromicron and Emerald Dwarf Danio, has captured the interest of many aspiring aquarists and compelled them to start a nano tank.

While these fish are incredibly hardy, we advise you to read this article first and equip yourself with the appropriate knowledge on how to take better care of this fish.

Emerald Dwarf Rasbora Stats

Scientific Name Danio erythromicron
Synonyms Microrasbora erythromicron (Annandale, 1918)
Family Cyprinidae
Genus Danio
Size of Fish 1 – 1.5 inches
Colors & Patterns
  • Salmon pink base
  • Reddish face
  • Emerald blue/turquoise/purple stripes
  • Big black dot on the base of the caudal peduncle
Diet Omnivore
Min. Tank Size 20 gallons
Temperature 68 – 76 F
pH 7 – 8
Hardness 2 – 10 dGH
Lifespan 3 – 5 years
Temperament Shy, skittish

Danio Erythromicron Background

The Emerald Dwarf Danio was discovered in 1918 and it was originally thought to be a microrasbora. Back in the day, the fish was identified as Microrasbora erythromicron, commonly known as Emerald Dwarf Rasbora.

Years of research and DNA sequencing, however, prove that it belongs to the Danio genus. Moreover, further molecular analyses have confirmed that the species is indeed closely related to the Danio margaritatus and Danio choprai. Thus, the Microrasbora erythromicron was transferred to the Danio genus and was given a new scientific name: Danio Erythromicron.

Due to these events, there is a lot of confusion about the exact name of the species. Many people still refer to the fish as Emerald Dwarf Rasbora. The aquarium trade also marketed the fish under several names, including “thick-banded purple zebra danio” and “cross-banded dwarf rasbora,” among others.

– Where Do They Come From?

The Emerald Dwarf Danio is one of the endemic species of Myanmar’s second-largest lake, Lake Inle. It is nearly 14 miles long and six miles wide. The water is brimming with stunning greenery, and it remains crystal clear.

The picturesque Lake Inle is an untouched corner of the world.  It is known far and wide for its beautiful floating gardens and wooden homes that perch above the water on rickety stilts.

– Are They Getting Extinct?

Thankfully, no. On the contrary, the ever-increasing pollution brought by the tourist trade and sewage from tourist accommodations might prove to be threatening one day.

Emerald Dwarf Danio Appearance

Emerald Dwarf Rasboras might be small, but their beauty always leaves a big impression. Although we can describe their beautiful details to you, nothing beats looking at them in person.

– How Big Do Dwarf Rasboras Get?

Emerald Dwarf Rasboras tend to stay less than two inches in length. A dwarf shrimp can look humongous next to them! Juveniles sold in pet stores are only a centimeter in length.

With the proper diet and water conditions, these tiny fish won’t take long to reach their maximum size.

– Distinct Features, Colors, and Patterns

As with other danios, the Danio erythromicron features the signature long and slender torpedo-shaped body. Males and females are pretty in salmon pink. Both sexes also have red-orange faces.

Covering their base color are several blue-green stripes that shimmer in the light, thus creating a brilliant display of colors. The stripes appear more turquoise rather than emerald, which makes the name a bit of a misnomer. On top of that, many males appear purple or blue rather than green.

Moreover, the fish lack any defense mechanism. What they do have is a large dot on both sides of their tails. This form of mimicry can help trick predators into thinking that they are always on the lookout.

– How Can You Tell If a Fish Is Male or Female?

Although they look the same as juveniles, you can distinguish males from females based on their color saturation once they grow older. Albeit smaller than females, adult males look more vivid. This applies to the fins, stripes, and base color. Males have red-orange fins, while their female counterparts have transparent ones.

Emerald Dwarf Danio Behavior and Temperament

The Emerald Dwarf Rasbora is not a true schooling fish. Don’t expect to see waves of these little fish swimming across your tank.

– Decoding Danio Erythromicron Behavior

Emerald Dwarf Rasboras are curious and active. You will see them buzzing around and investigating every nook and cranny of the tank. Since the fish are not true schoolers, you are more likely to find them in a loose cluster instead. Sometimes they go their separate ways and do their own thing. These danios can be shy too and will dash for hiding if someone passes by the tank unannounced.

Little skirmishes can happen between males. They will chase and nip each other to establish a hierarchy. On a positive note, you can minimize the aggression by keeping them in a large group. That said, you may need to buy as many of these danios as you can, ideally 15 or more.

Inappropriate water parameters, degrading water quality, overcrowding, or having a scant number of females can also drive male danios cranky. Fortunately, in-fighting does not result in serious injury.

– Are Emerald Dwarf Rasboras Aggressive?

No, they aren’t. These danios are peaceful. But without the safety of a school, it should come as no surprise how skittish and shy they are toward others. It will take some time for Emerald Dwarf Rasboras to get along with other calm-natured species and get real comfortable with them. Until then, these danios prefer to stick with their own kind.

Emerald Dwarf Rasbora Tank Mates

There is only one rule to follow when choosing tank mates for the Emerald Dwarf Rasbora: avoid large, aggressive fish that will eat your danios, as well as tropical fish that require warm water. While your beautiful danios will not bother other fish, any larger species may assume they are an eat-all-you-can buffet.

Beyond that, you are free to choose which freshwater fish to stock with your Emerald Dwarf Rasboras. You can add devarios, small barbs, and freshwater snails. Choosing species that are native to Lake Inle is also a fantastic idea:

  • Celestial pearl danio (Danio margaritatus)
  • Lake Inle danio (Devario auropurpureus)
  • Red dwarf rasbora (Microrasbora rubescens)
  • Sawbwa barb (Sawbwa resplendens)

By doing so, you can rest assured that all the fish have similar water requirements and benefit from the same tank setup. As a bonus, you can create a miniature representation of the stunning Lake Inle!

Emerald Dwarf Rasbora Care

This species can live anywhere between three to five years in captivity. The better care you provide for your danios, the higher the odds of reaching their maximum lifespan.

– Emerald Dwarf Rasbora Diet

Emerald Dwarf Danios are omnivores. In the wild, they eat zooplankton, algae, and other critters small enough to fit into their mouth.

The omnivorous danios will learn to accept commercial dried feed, but most of the time, they prefer meaty food. What’s more, they seldom rise to the surface to get food. Therefore, it is better to provide them live or frozen fare, such as brine shrimp, bloodworms, mosquito larvae, and daphnia.

Providing your danios such a diet ensures the best coloration and encourages them to breed. Algae wafers should also be given from time to time to satisfy their need for vegetable matter.

– Water Parameters and Maintenance

Emerald Dwarf Rasboras prefer cool temperatures in the range of 68 to 76 F. This species doesn’t thrive in acidic water, so the pH level should stay alkaline. The hardness should not exceed 10 dGH.

  • Temperature: 68 – 76 F
  • pH Levels: 7 – 8
  • Hardness: 2 – 10 dGH
  • Water changes: 10 to 20 percent each week

Since there is no rain to refresh the water and carry away contaminants, the best you can do to dilute toxins is to change the tank water 10 to 20 percent every week. Remember, nano tanks.

– Health Risks

All Danio species are hearty, but they can still acquire certain diseases when the water is contaminated with bacteria, nematodes, and fungi via different means. Velvet and Ich are two of the most common diseases that affect Emerald Dwarf Rasboras. On the bright side, these diseases are preventable as well as treatable.

Emerald Dwarf Rasbora Breeding

How do you breed the Emerald Dwarf Rasboras? In most cases, you won’t have to get involved! These eager spawners will breed without human intervention.

As long as you condition the fish with a high-protein diet and set up their habitat as suggested below, they will procreate in no time.

You may also arrange a breeding tank to maximize the survival rates of the fry. Duplicate the setup of the main tank. Only this time, you should use an air stone and a sponge filter. The latter isn’t strong enough to harm your fry but is effective enough to cycle water.

– How Do Emerald Dwarf Rasboras Care for Their Fry?

When a female is ready to spawn, she will scatter 30 eggs or more, which the male will fertilize. The viscous eggs will cling onto plants and hatch within three days. Emerald Dwarf Rasboras don’t provide parental care to their young. You should get rid of the parents after fertilization lest your fry will get eaten.

The newly hatched fry will obtain nourishment from the egg sacs for the first four days. Let them grow in the breeding tank for up to eight weeks. Feed them infusoria and switch to Artemia nauplii when they are large enough to accept them. You may introduce the young fish into the main tank as soon as they have grown larger than their parents’ mouths.

Emerald Dwarf Rasbora Tank Setup

The ideal tank setup for Emerald Dwarf Rasboras replicates Lake Inle. Mimicking their natural habitat ensures the health and wellbeing of your fish. But before you add them, you must run a newly set up tank for at least three days.

– Tank Size

A lot of people are asking, “How many Dwarf Rasboras can I put in a 10-gallon tank?” At the very least, you can keep a shoal of 15 to 20 fish and still provide everyone with plenty of room to play around.

Better yet, upgrade to a 20-gallon tank so that you can add more danios and get more creative with your setup. If you wish to include a few other species of danios and create your own little Lake Inle, it would be wise to go for a much larger tank.

If you are new to fishkeeping, you should start around 25 gallons. A nano tank can be a challenge to maintain for the first-timer. The water condition can change rapidly when there is less water.

– Substrate

We recommend dark aqua soil for your planted tank. The organic decomposition of the soil releases carbon dioxide to nourish plants and encourages bacteria colonization that stabilizes the tank environment. As a result, it offers a higher success rate for growing plants that would otherwise need CO2 injections.

Moreover, a soil-based substrate offers a minimalist look, thus making the color of your fish and plants pop. At the same time, it replicates the loam substrate of Lake Inle.

– Plants and Decorations

Furnish the tank with a plethora of plants, occupying at least 50 percent of the space. Emerald Dwarf Rasboras love it when they live in a lush jungle. With plenty of places to hide, they will feel comfortable and secure as soon as they arrive in their new home.

Living in a sparsely decorated tank will aggravate their skittish behavior and put them under constant stress. Likewise, it is an invitation for algae to grow. Beginners, however, should choose “easy” plants that will work with low CO2 conditions. These include plants, such as:

  • Anubia species
  • Dwarf sagittaria
  • Java fern
  • Java moss
  • Marsilea species
  • Ludwigia Repens
  • Pearlweed
  • Red or green lotuses
  • Rotala rotundifolia
  • Sword plants
  • Vallisnerias
  • Water sprite
  • Water wisteria

You may also add ceramic ornaments and slate structures if you like. Be careful when adding driftwood. Natural driftwood may release tannins that could stain the water, which is something these fish could not tolerate much.

– Equipment

Small tanks can be a breeze to set up, but they can be more difficult to manage than larger ones. Regardless, you will need the following equipment for things to run smoothly.

Filter: Aquatic plants will work for your tank’s health but for the best results, use external filtration. A hang-on-back system is a popular choice for nano tanks; it doesn’t consume a lot of space and provides mechanical, biological, and chemical filtration.

Lighting: Another important consideration for a planted tank is lighting. Apart from promoting plant growth, it makes your fish look brighter.

Testing Kit: Be sure to invest in an aquarium water test kit and always keep tabs on these parameters. Being updated with the most current state of your aquarium is vital should you wish to provide optimal care for your fish.


The Emerald Dwarf Rasbora is a fantastic choice for rookies jumping into the aquarium hobby, but a 10-gallon tank poses more difficulty for the beginning aquarist.

Therefore, we suggest you opt for a larger aquarium to stave off potential problems regarding the water condition. And remember:

  • Dense vegetation is a must for the Emerald Dwarf Rasbora. Since you are aiming for a jungle-like tank, choosing the right substrate is also a crucial element to ensure plant health and, of course, the overall beauty of the plants.
  • Maintain the recommended parameters and perform 10 to 20 percent water changes once a week, especially if you are pushing the population limit of your tank.
  • Emerald Dwarf Rasboras are a peaceful species, but males will spar against each other at one point to establish a pecking order. Fortunately, the fighting does not result in serious injury.
  • These danios are likely to be intimidated and outcompeted by large fish, but the presence of active, similar-sized species can help reduce their shyness.
  • This species is eager to breed, but placing the parents in a controlled environment ensures survivability for the fry.

We hope this care guide has delivered enough information to get you started. If you have questions left unanswered, feel free to ask us!

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