Freshwater Fish

Emerald Microrasbora (Celestichthys erythromicron): Aquarium Care Guide

Emerald Dwarf Rasboras are a beautiful freshwater fish that are greatly underrated. For whatever reason, they just aren’t that popular.

And we didn’t get it.

This species is peaceful, easy to care for, and beautiful. Watching a group of them swim around your aquarium is a sight to see!

This guide will teach you everything you need to know about proper Emerald Dwarf Rasbora care. By the time you finish reading it, you’ll be ready to have something yourself.

Species Summary

If you want to fill your aquarium with color and life, consider the emerald dwarf rasbora! Scientifically known as Celestichthys erythromicron, these are tiny fish with big personalities.

In a well-decorated environment, these freshwater fish are very active and curious. They can often be seen playing or saving with others.

The emerald dwarf rasbora is endemic to Inle Lake in Myanmar. This clear, shallow lake is rapidly changing, putting wild populations at risk. Fortunately, this species is eager to reproduce, resulting in healthy numbers in the aquarium trade.

Thanks to their small size and beautiful color, these fish are great additions to tanks large and small.

Average size of the emerald dwarf rasbora

The average adult size of the Emerald Dwarf Rasbora is between 1 and 1.5 inches long. These fish are not very large, which makes them a great species for nano tanks.

When you buy them young, they will likely only be half an inch or so! These freshwater fish have a constant growth rate and do not take long to reach their maximum length.

Author’s Note: Adult males are generally smaller than females. However, its small size still makes it difficult to tell the difference.

Life expectancy

The lifespan of a healthy Emerald Dwarf Rasbora is around three to five years. This is a pretty reasonable life expectancy for a fish of this size.

Because they are so small, these fish need pristine living conditions to stay healthy. Without proper care, they can become prone to various diseases and die long before reaching their life expectancy.


Emerald Dwarf Rasboras may be small, but they still have lots of beautiful details that turn heads! While we can describe it to you, you really need to see them in person.

These fish have long, thin bodies. On their heads, you’ll notice large glowing eyes and semi-transparent scales around the gill plate.

The body of this species is typically coral pink or orange. These colorful fish stand out beautifully against a dark or plant-covered background.

Covering that base color are several thick bands of emerald green. The color shimmers in the light, creating a beautiful display as the fish swim around the tank. Stripes may vary slightly in color. Some will appear more purple or blue.

At the base of the tail, these fish have a large point on both sides of the body. This point is a form of mimicry. It looks like an eye, which can deceive predators in the wild.

Author’s Note: There are some notable differences between males and females beyond size. Males generally have more vibrant colors. This applies to the base color, stripes, and fins. The males have red or orange fins. Meanwhile, the fins of the females are usually transparent.

Emerald Dwarf Rasbora Care

Emerald Dwarf Rasbora care is fairly easy as long as you are aware of your main tank and water requirements. This is a species that can adapt well to a variety of conditions without any problems.

With that said, you have to be serious about caring for them if you want them to thrive! Emerald Dwarfs need stable tank conditions, a well-decorated environment, and a high-quality diet to live a healthy life.

Follow the basic care guidelines below to keep your fish in tip-top shape!

tank size

As a dwarf-sized species, these fish don’t need a lot of space to stay happy. At a minimum, you should keep Emerald Dwarf Rasboras in a 10-gallon tank. That’s adequate for a fairly healthy collection of fish.

However, we recommend keeping them in a 20 gallon tank for best results. The extra space will allow you to keep a school of 24 to 30 fish and give everyone more room to swim.

water parameters

The natural habitat occupied by emerald dwarf rasboras is unique. They come from crystal clear waters, but Inle Lake rests in a valley that is about 900m above sea level.

Because of this, Emerald Dwarf Rasbora prefers cooler temperatures and neutral pH levels. This species does not do well in acidic water, so it is best to err on the side of caution and aim for a slightly alkaline pH balance.

Stick to the following water parameters and your fish should have no trouble acclimating to your tank:

  • Water temperature: 70°F to 75°F
  • pH levels: 7.0 to 8.0
  • Water hardness: 2 to 10 dKH

Author’s Note: Be sure to invest in an accurate and reliable aquarium water test kit to monitor these parameters. Being informed about the status of your aquarium is incredibly important if you want to provide top-notch care.

decorate your tank

Dense vegetation and lots of decorations are a must for this species, as emerald dwarf rasboras need places to hide. They use plants, rocks, and other decorations for shelter.

When kept in a sparse tank, they can exhibit more skittish behavior (and live in a constant state of stress). A more natural and lively environment gives these fish more confidence to swim.

Get a healthy mix of live plants to support this behavior. You can use any plant that can survive in the natural living conditions of this species (check these care guides to be sure). Aim for leafy plants and floating plants. These fish will hide and play among the vegetation.

You can also add driftwood. However, avoid any natural driftwood or leaf debris that can release tannins. Remember, these Emerald Dwarf Rasboras come from clear waters. Tannin stained water is not something they will tolerate very much.

At the bottom of the aquarium, use a dark-colored substrate. This will not only bring out its color, but also mimic the loamy substrate of Inle Lake. Use fine sand instead of gravel for safety.

Another important thing to consider is filtration. These fish prefer to stay in large groups, which creates a lot of waste. Choose a filtration system with a water flow rate that is four to five times the volume of the tank. This ensures that the tank is efficiently cycled to remove ammonia and nitrates.

Possible common diseases

Emerald Dwarf Rasboras can suffer from all the standard freshwater fish diseases. This includes Ich, parasitic infections, and swim bladder disease.

Ich is a common but dangerous disease that is usually caused by poor water conditions. Itchy white spots form all over the body. If left untreated, fish can die from Ich. To make matters worse, it is highly contagious and can quickly spread throughout the tank.

Skin flukes are another concern. Flukes are small parasites that attach to the skin or gills. The infection could cause shortness of breath, so it is important to treat the disease as soon as possible.

Swim bladder disease is one of the most alarming ailments these fish can experience. The bacteria damage the swim bladder, which affects the fish’s buoyancy and swimming ability.

Author’s Note: The good news is that treating all of these diseases is quite simple. Over-the-counter medications and quarantine should usually address the problem and return your fish to good health.

Food and Diet

Emerald dwarf rasboras are omnivorous. They will accept most commercial flake or pellet foods. These fish are also passive algae eaters.

Dry foods should be the main source of nutrition. Choose foods that are nutritionally balanced for good health. You can also look for color formulas that help bring out the natural vibrancy of these fish (be careful when researching these brands, though).

Emerald Dwarf Rasboras can get fussy at times. While they will accept dry foods, they generally prefer high-protein snacks much more. Therefore, it is a good idea to provide them with some from time to time. It will provide enrichment and help them stay healthy!

You can feed them live or freeze-dried food. Some foods to try are daphnia, bloodworms, and brine shrimp.

behavior and temperament

As a peaceful species, the Emerald Dwarf Rasbora gets along with most other fish.

However, they prefer to stay with their own kind. They are very social and do best in large groups.

Emerald dwarf rasboras are a schooling species. This means that the fish will group together and swim together, but will also go off and do their thing from time to time.

Author’s Note: You may see some in-fighting between the males. Males often train with rivals, resulting in clipped fins here and there. In most cases, the fight will not result in serious injury. Furthermore, it does not go beyond the group of species.

For the most part, these fish are quite active and will swim around exploring the tank throughout the day. They are very curious creatures, so you will see them buzzing through the plants and looking at every nook and cranny of the aquarium!

tank mates

Beyond fish of the same species, Emerald Dwarf Rasboras can get along with most peaceful freshwater species (and many other types of rasboras). You don’t have to worry about aggression from the Emerald Dwarf Rasboras, but you will have to worry about them becoming food for someone else.

It is important to avoid any large or remotely aggressive fish! This species does best with fish of similar size.

You can also search for tankmates that come from the same region. There are many other species native to Inle Lake in the fish trade.

Here are some good tank mates for the Emerald Dwarf Rasbora:

  • Sawbwa Pick
  • Celestial Pearl Danio
  • danian glow
  • red dwarf rasbora
  • small types of catfish
  • Darius Hysginon
  • cherry shrimp
  • Most freshwater snails


Emerald Dwarf Rasboras are eager breeders. In pristine conditions, these fish will breed frequently without any intervention. They are egg spreaders, but they don’t exhibit any parental instincts at all (which makes things a lot easier).

If you want to maximize the survival rates of baby fish, it is best to raise them in a controlled environment.

Create a separate breeding tank and fill it with well-cycled water. Add spawning mops or leafy plants. Then add a joined pair. You can also add a group consisting of two men and several women.

Author’s Note: It is worth noting that more individual fish will increase the risks of the eggs being eaten.

Protein-rich foods should be provided at this point. Spawning should happen relatively quickly. The females will lay around 30 eggs in the entire tank. They are slightly sticky so the eggs can stick to leaves or decoration.

The eggs take about 72 hours to hatch. The fry will survive in the egg sac for another three to four days before becoming free-swimming. You can then provide infusoria or powdered fish food until they are ready for baby brine shrimp.


Emerald Dwarf Rasboras are a wonderful freshwater species that deserve much more attention from the fish community. Their beauty and ease of care make them a no-brainer!

We hope this guide has done an effective job of teaching you the basics of caring for these fish. If you have any other questions that we haven’t answered, don’t hesitate to ask us!

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