Emerald Dwarf Rasbora: Complete Care Guide

a group of fish swimming in an aquarium
Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: July 13, 2024
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Attention aquarium enthusiasts! Discover the emerald dwarf rasbora, a unique treasure for your nano freshwater aquarium. This fish captivates with its unique and enchanting beauty, making it a hidden gem waiting to be unveiled. Our comprehensive care guide reveals the secrets of caring for this stunning species in your home aquarium. Dive in and transform your tank into an enchanting aquatic paradise. Keep reading to expand your expertise.

Article Summary

  • Emerald dwarf rasbora have a distinctive feature of a large black dot at the base of the tail on both sides, serving as a deceptive technique against predators.
  • It is recommended to have at least a 20-gallon tank for 10 Emerald Dwarf rasboras.
  • A balanced diet including commercial dry food and vegetable matter like algae wafers is advised.

Species Overview

Common namesEmerald dwarf rasboras, Emerald dwarf danio
Scientific nameDanio erythromicron, Celestichthys erythromicron
SpeciesD. erythromicron
Lifespan3-5 yrs
DistributionAsia, Lake Inle
ColorGreen, blue, purple, silver
Minimum tank size20 gal
Place in the tankTop
Care LevelModerate

You might notice this species has two scientific names. This is because the emerald dwarf rasboras are closely related to the emerald dwarf danio. In fact they are so close that their DNA has had to be molecularly analyzed for scientists to conclude they should be in the Danio genus, but many still call them by their original genus.

History and Background

This species has only been part of the aquarium hobby for 2 decades, likely due to its isolated environment. Despite being fairly new to the aquarium world it has made a big impact and changed the world of nano tanks.

What is an emerald dwarf rasbora ?

They are a tiny fish species that is perhaps underrated in the aquarium hobby despite having beautiful coloring. This hardy fish has a high activity level and will add lots of color to your tank (and not just because they’re green).

Where did the emerald dwarf rasbora come from?

Emerald dwarf rasboras are a freshwater fish that are native to lake Inle, a body of water in Myanmar. They share their habitat with Lake Inle danio which are a well known dither fish. The natural habitat of this fish is unique in that the lake rests 900 meters above sea level as a crater lake. Crater lakes naturally have more acidic water, which is why these fish generally prefer higher pH ranges.


Dither fish are bright colored fish used to draw shy fish out of their hiding spot. The presence of a dither fish indicates that there are no predators around or else it wouldn’t be risking being seen.


The bright green appearance of this fish is definitely what draws most hobbyists to it. The slightly metallic sheen of their scales will catch the aquarium lights as they swim by. Their deep green color will also contrast when compared to the plants in their aquarium.

What do emerald dwarf rasbora look like?

Emerald dwarf rasboras have a slender body that has a base color of silver or white covered by several, thick emerald green stripes. Their red or orange fins are nearly translucent and hard to see when they are swimming, fin colors are generally more prevalent on male adult fish. One of the most noticeable features is the large black dot at the base of the tail on both sides of their body. This is actually a technique used to trick predators into thinking that their tail end is actually their head.

How big does an emerald dwarf rasbora get?

Emerald dwarf rasboras are tiny fish and will grow to a maximum of 1.5 inches, but generally grow to be 1 inch on average.

How fast do emerald dwarf rasbora grow?

It takes roughly 6 months for young fish to reach their adult size.

Temperament and Tankmates

beautiful fishes swimming in a planted tropical freshwater aquarium
An Aquarium With Different Fish Species

A very calm species, it is unlikely that your rasbora will give you any issues when it comes to compatibility with other tank mates.

How many Dwarf Rasbora per gallon?

You should try to keep at least 10 emerald dwarf rasboras in your 20 gallon tank. In other words, roughly 2 gallons per fish.

How many emerald dwarf Rasboras should be kept together?

As a shoaling fish species it is important that you have multiple emerald dwarf rasboras in your aquarium. As they are tiny you should try to keep them in schools of 10 and above, with the best results being when they are kept in schools of 20-30.

What fish can live with emerald dwarf rasbora?

As a peaceful species you won’t have much trouble finding tank mates that emerald dwarf rasboras will cohabit with, however it is challenging to find other fish that won’t call your emerald dwarf rasboras a meal.

Compatible tank mates

  • Emerald dwarf rasboras-as a social species these small fish do best when kept with others of their kind. You will see the most personality development when keeping multiple of this shoaling species together.
  • Red dwarf rasbora-this peaceful fish looks almost identical to emerald dwarf rasboras in everything except color. They will add a wonderful color combination to your green tank.
  • Cherry Shrimp-a peaceful and hardy species, cherry shrimp will go about their own business and are one of the best tank mates for emerald dwarf rasboras.
  • Celestial Pearl Danio-a small fish that won’t get much larger than your emerald dwarves they are both peaceful and do well together.
  • Freshwater snailsmystery and nerite snails will not have much issue with emerald dwarf rasboras and will be happy to let them swim overhead while crawling along the bottom.

Tank mates to avoid

Any aggressive fish that are larger than these freshwater fish are generally bad tank mates as they will likely eat your rasboras.

  • Goldfish-well known for their voracious appetite this fish will make short work of your tiny rasbora as well as majorly foul up its tank.
  • Oscars-another large fish that is known for displaying aggressive behaviors and will likely eat your rasboras if given the chance.
  • Cichlids-while not all cichlids are aggressive, the majority of them won’t hesitate to eat your rasbora.
  • Crabs-while they won’t eat your fish, most freshwater crabs are known to be territorial and they will likely bully your rasboras. Additionally, they are messy eaters and will quickly foul your water quality.
  • Barbs-a larger fish that can potentially bully your school of rasboras.

The larger your shoal of rasboras the less likely other fish will try to bully it, however that won’t phase aggressive fish such as the ones listed above.

Tank Requirements

A Planted Aquarium
A Planted Aquarium

This fish has extremely easy tank requirements and is an excellent choice for beginners. The main task is keeping the tank system clean, but as long as it’s not overcrowded smaller tanks tend to be easier to upkeep.

Water Parameters

Tank Size>20 gal
Water typefreshwater
Water temperature70-75
Water pH7.0-8.0
Water hardness2-10 dKH

Tank setup:

What kind of Substrate to use?

It is recommended to use fine sand as your aquarium substrate. Not only is this similar to their natural habitat at Lake Inle, it will also allow you to add aquatic plants to the tank. If you really want to spotlight the coloring of this fish be sure to use dark colored substrate.

Do I need a Filter?

It is necessary to have a properly sized filtration system for your tank to help maintain proper water parameters. In other words, the filter that will work for nano tanks will not have enough water flow or circulation to make a healthy environment for larger species living in a big tank.

Should I add a Pump?

As there is a lot of plant growth in rasbora tanks we suggest using a pump or air stone to increase water circulation and ensure that your aquarium is being properly oxygenated.

Is a Water heater necessary?

As a tropical species that prefers warm water, you will need to add a water heater as well as an aquarium safe thermometer to your aquarium to maintain proper water temperature range.

How much Lighting is too much?

This fish doesn’t have super stringent lighting requirements, however it is a good idea to research whatever leafy plants are going in your aquarium and what lighting they require.

All fish should have a regular light cycle including 12-16 hours of darkness and 8-12 hours of light to help establish a regular REM schedule and promote a healthy life.

Should I add Plants?

Having an aquarium with dense vegetation is the ideal tank setup when it comes to emerald dwarf rasboras. Many hobbyists in the aquarium trade will use a larger tank to create beautiful floating gardens using floating plants, natural driftwood, and leafy plants. Not only does this create a stunning display but it will also give your emerald dwarf rasboras an enriching environment to grow up in.

Diet and Health

Bloodworms in Plastic Container
Bloodworms in Plastic Container

For their diet emerald dwarf rasboras prefer high protein meals from a variety of sources including fish, small crustaceans, and insects. It is important to provide a well balanced and varied diet to ensure that all nutrition requirements are being met. Remember it is more important to have a high quality diet than a high quantity of food.

What do emerald dwarf rasbora eat

In their natural habitat in Lake Inle these freshwater fish will eat a protein rich diet including foods such as mosquito larvae, insects, small crustaceans, fish eggs, and algae.

What to feed emerald dwarf rasbora?

In a controlled environment such as your aquarium you should try to mimic the natural habitat diet of rasboras as closely as you can. This means many high protein foods such as brine shrimp, bloodworms, and daphnia. These protein options can be live, frozen, or freeze dried foods.

In order to achieve a balanced diet your emerald dwarf rasboras should also be given commercial dry food and vegetable matter such as algae wafers. Dry food that is specially formulated for this fish will contain any vitamins and minerals they need as well as help brighten their coloration.

How often to feed emerald dwarf rasbora?

Feed your fish once daily, this can be combined with feedings for other fish species in your aquarium or a separate feeding in a different part of the aquarium for just rasboras and their own kind.

How much to feed emerald dwarf rasbora?

Feed your fish in accordance with the 3 minute rule. This states that you are allowed to feed your fish however much food they will eat in the span of three minutes. This will allow them to eat as much as they are hungry for without having the risk of overfeeding which can lead to bloating, constipation, and other gastrointestinal problems.

Common diseases of emerald dwarf rasbora

Swim bladder disease

Commonly displayed as an imbalance fish you might notice them having trouble swimming or leaning to one side. Treatment depends on the root cause such as constipation (addition of fiber to diet), bacterial infection (broad spectrum antibiotic), or genetic defect (no cure). Additionally, you can move the fish affected by swim bladder disease to a quarantine tank and lower the water so that they won’t have to fight as hard to stay upright. This will improve quality of life and decrease stress.


Similar to ich in appearance this disease will cause white spots and patches to appear on the body of your fish. It is generally caused by poor water conditions (especially high water temperature), improper diet, or overcrowding. To treat lower the temperature of the water and add broad spectrum antibiotics.

Parasitic Infections

All freshwater fish are susceptible to tiny parasites that latch on to their fins, gills, or intestines. It is hard to identify a parasitic infection but common symptoms include lethargy, loss of appetite, and irate or abnormal behavior. To treat parasites you will have to purchase an anti-parasitic medicine.

How long do emerald dwarf rasbora live?

This freshwater fish generally lives 3 to 5 years in ideal tank conditions. In terms of the aquarium hobby, this is a fairly short lifespan and commitment for a fish.


Fortunately, despite their diminishing environment due to environmental conditions these fish are relatively easy to breed in captivity. If you’re not planning to breed them you can allow them to reproduce and let other tank inhabitants eat the eggs as an extra snack.

Can you breed an emerald dwarf rasbora?

It is quite easy to breed them, and more often than not they will do it on their own. For those that don’t want them to breed either ensure that the tank is all female, or don’t remove the parents after they lay their eggs-other tank mates will eat them.

How to breed emerald dwarf rasbora?

These fish are egg layers and don’t have any parental instincts. It is best to provide a separate breeding tank for the young fish so that you can provide optimal care. Within the breeding tank add leafy plants or spawning mops for the female fish to lay their eggs in. Once the tank is set up you can add a mating group into the aquarium, this usually consists of two males and multiple females, or an already bonded pair of an adult male and female.

Begin feeding the fish you want to spawn a high protein diet, you should very quickly notice mating rituals taking place and the female beginning to lay eggs.


The one time you might see aggression out of this species is when they perform their mating dance. This is often interpreted as the male chasing the female and occasionally nipping her fins.

Eggs will be scattered about the tank on various surfaces and will hatch in roughly 3 days. Three to four days after that the fish will become free swimming. After the fish fry begin to swim on their own you can offer powdered fish fry or infusoria, after another week they should be large enough to begin eating baby brine shrimp. Baby brine shrimp, while one of the most commonly used fish fry foods, is an important part of young fish’s diet and provides them with the protein they need to grow.

Emerald dwarf rasbora FAQS

Are emerald dwarf rasboras extinct?

No, this species is only found in one specific lake in the whole world. Any wild populations that you find outside of Lake Inle are from aquarists that have released fish from their aquariums.

Are emerald rasboras aggressive?

No, this species is not an aggressive fish, though they may seem a bit stand-offish because of their preference to stick with their own kind. In reality this fish is peaceful and sociable.

Are emerald rasboras beginner friendly?

Yes, they are a hardy species that does well in beginner tanks, the hardest aspect of care comes when choosing their tank mates.

Do emerald rasboras need plants?

It is strongly encouraged to provide these fish with plants in their aquarium as it will increase their health by giving them places to explore, hide, and play in.

Is the emerald dwarf rasbora for you?

If you’re looking for a small and brightly colored fish the emerald dwarf rasbora is an excellent choice. They are active and will provide hours of eye-catching entertainment.


In conclusion, these fish are an excellent addition to any small freshwater aquarium that needs extra color.

Featured Image – Cantospira, CC BY-SA 4.0, via Wikimedia Commons

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