Blue Green Chromis: Species Profile & Complete Care Guide

Blue green chromis
Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: July 13, 2024
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If you’re searching for a new addition to your reef aquarium or looking to add vibrant color to your tropical saltwater world, the blue green chromis is an excellent choice. This peaceful, reef-compatible fish is perfect for beginner saltwater aquarium hobbyists, offering endless entertainment for years. Although the blue green chromis is typically low-maintenance, it has specific care requirements that are important to understand!

Article Summary

  • Blue Green Chromis (Chromis viridis) is a peaceful and reef-safe fish suitable for beginner saltwater aquariums.
  • They are omnivores and require a varied diet, including live and frozen foods, flakes, or pellets.
  • Blue Green Chromis require a minimum tank size of 30 gallons, with appropriate water parameters, including temperature, pH, and salinity.

Species Overview

Common namesBlue green chromis, Blue Green Damselfish, Blue Green Puller
Scientific nameChromis viridis
Size1-4 inches
Lifespan8-15 years
FamilyPomacentridae
GenusChromis
DistributionIndo-Pacific
ColorBlue/green
DietOmnivores
TemperamentPeaceful
Minimum tank size30 gallons
Place in the tankMiddle/top water column
Care levelBeginner
BreedingModerate to Difficult

History and Background 

Though it is unclear when the Chromis viridis first entered the aquarium hobby the tropical fish was first described in 1830 and is now a favorite of hobbyists everywhere.

Origin 

The blue green chromis is a saltwater fish originally found in the Indo Pacific Ocean in its more tropical waters. Generally found near lagoons and coral reef areas you can find them in the waters east of the Philippines, eastern Australia, and in New Guinea. The range of this saltwater fish has expanded all the way to Madagascar and Hawaii likely due to aquarists deciding that they no longer want to keep them and releasing them into the wild.

Natural Habitat

In the wild blue green chromis fish form a small school and can be found darting through reefs and rocks. They enjoy an aquarium that replicates their natural environment with lots of corals, rocks, and enough swimming space for each small group.

Appearance 

A blue green fish
(1) Close-up image of Blue Green Chromis

With their iridescent coloring it’s not hard to see why these fish are popular.

What do blue green chromis look like?

This saltwater fish is generally one to four inches long, with the largest being roughly five inches long. They are well known for their pale green and blue coloring depending on the light. Unlike others in the damselfish family they have a forked tail and are generally very streamlined. They also have small protruding bumps on the back and bottom edges of the eye.

Mature males will change their coloration to a pale yellow when they are ready to start building a nest at the beginning of the spawning process.

Some individuals have dark markings on their fins or body making them stand out from others.

Color Variety

Despite its name being Chromis viridis (green chromis) this species has both blue and green coloring depending on its environment. In fact it’s color can even shift as you watch it swim from one side of the tank to the other based on lighting.

FUN FACT

Some people mistake the blue green chromis for the blue reef chromis even though they are completely different fish. The blue reef is generally a darker blue and was bred in captivity for the first time in 2016!

How big blue green chromis get?

On average your blue green chromis will be one to four inches, with those on the larger side coming in at around five inches. Their small size makes them easy to keep in a school in your reef tank.

Why is my blue green chromis turning black?

While seeing your blue green fish begin to turn black can be frightening it is not the end of the world. Most often this is a result of stress, or an attempt to camouflage themselves with their environments. This behavior can be caused by transferring tanks, feeling unsafe, or bad water parameters.

After establishing that your water quality is good, dim the aquarium lights and check for any other stressors in the aquarium. These can be a high flow rate, loud sounds (especially if your aquarium is in a common area), or a tank mate that is a bully. Watch your fish and see how it responds to each of these stressors and eliminate them one by one.

TIP

It is also worth noting that the blue green chromis comes in a wide variety of blues and greens that is largely dependent on the aquarium lighting. If your fish is dark blue or purple it is worth changing light levels to see if you can achieve the desired coloration.

Temperament and Tankmates

Saltwater fish tank with corals and fish
A Beautiful Reef Tank

An easygoing and safe coral reef fish is hard to find, luckily the blue green chromis does well in both reef and fish only tanks.

Can chromis be aggressive?

Unlike other damselfish the blue green chromis is known to be a peaceful species that does well with other peaceful species of similar size. They are reef safe and are a great addition in your saltwater aquarium.

Be aware that some fish may try to snack on small invertebrates, especially juvenile shrimp and crabs, but generally won’t bother adult ones.

How many blue green chromis should I keep?

Since this species prefers to live in a school you should try to keep at least six or seven of them per tank. However, a minimum of four fish is needed for them to form a school and be happy. You might notice some aggression when introducing the group to each other, this will quickly be sorted out as group hierarchy and pecking order is established.

Can Blue Green Chromis live alone?

No, this saltwater fish will be happiest in a school as it is generally considered a shoaling species (though some individuals may prefer to be alone). However, you can keep only blue green chromis in your tank without any issues.

What fish can live with blue green chromis?

As a peaceful fish that is adaptable to a large range of water parameters, most other species of a similar size- such as clownfish and blennies- will do well with the blue green chromis. If you need some suggestions to get you started we’ve included our top 5 and why below.

Compatible tank mates

  1. Clownfish-similar in size and another damselfish the clownfish will initially show some aggression to individual chromis when they are in a school there aren’t many problems.
  2. Royal Gramma Basslet-another charming species, you’ll likely see these two species swim side by side.
  3. Blennies-a similar size fish blennies are hardy and generally hover near the bottom of the tank making them excellent companions for your chromis.
  4. Yellow Watchman Goby-like the blenny this species is a similarly sized, bottom dwelling fish that can cohabitate with your chromis.
  5. Adult Ghost Shrimp-While this species is an excellent companion it can also make an excellent snack for your chromis, use with caution.

RECOMMENDATION

Adult invertebrates such as crabs or snails are also excellent tank mates for this fish as they have protective shells.

Tank Requirements

Fish Tank With Tropical Coral Reef Aquarium
Fish Tank With Tropical Coral Reef Aquarium

The blue green chromis is traditionally found in lagoons (up to 12 meters deep), and shallow water reef areas. Tank setup should mimic these conditions.

Blue green chromis tank setup

What kind of substrate do I need?

For these fish soft substrate that they can burrow in is best. You will likely already have sandy substrate if you have a reef tank.

Gravel, small rocks, or bare bottomed tanks don’t work well for these fish as the male builds nests in the substrate during spawning season.

Do Blue green chromis need a filter?

Despite their small size you need a solid filtration system for blue green chromis to keep pristine water conditions. Despite being hardy fish they are sensitive to nitrate and ammonia build up, something that can occur quite rapidly when they are kept in a large school.

What kind of pump should I use for a blue green chromis tank?

To take proper care of your blue green chromis and other fish in your home aquarium you should ensure that you have proper water circulation. The easiest way to do so is with the addition of a pump. However, as these fish are found in lagoons and shallow coral areas it is best not to have a fast flow.

Should I use a water heater?

As the blue green chromis is a tropical fish we strongly recommend using a water heater to maintain ideal temperature ranges (72-80°F).

What kind of lighting do blue green chromis like?

This species isn’t picky when it comes to lighting and whatever lighting your coral needs will be fine. However, some aquarists like to experiment with lighting to compliment the coloring of this fish.

Do blue green chromis like a heavily planted tank?

This species is reef safe and prefers the crevices of live rock and coral to a heavily planted tank. However, some planted areas are not a bad idea, and will encourage grazing amongst your fish.

Tank Size

For one blue green chromis you need a minimum tank size of 30 gallons. However, as this is a schooling species (with a recommended school size of 6) you should keep your group of blue green chromis fish in at least a 55 gallon tank to ensure they have enough swimming space.

Water Parameters 

Tank SizeMinimum of 30 gallons
Water TypeSaltwater
Water Temperature72-82, 75-78 is ideal
Water pH8.1-8.4
Water hardness8 to 12 dKH
Salinity1.020-1.025 specific gravity

Diet & Health

Bloodworms in Plastic Container
Bloodworms in Plastic Container

This low-maintenance fish is perfect for beginner fish keepers, or the aquarist on the go.

What to feed blue green chromis?

In the wild the blue green chromis diet consists of everything you might find in coral reefs ranging from krill to algae to shrimp. They are considered omnivores so it is important to give your blue green chromis a varied diet to ensure they are getting all the vitamins they need.

We recommend a diet of live and frozen foods with supplemental commercial foods such as flakes or pellets. Mysis or brine shrimp, blood worms, or algae flakes should be included in their varied diet. 

TIP

If you really want to make your blue green chromis fish’s colors pop, look for food that is specifically made for brightening fish colors. This food often contains special vitamins and minerals that are targeted towards certain fish like the blue green chromis.

When to feed blue green chromis?

You should be feeding your fish small meals throughout the day to replicate the natural hunting conditions as well as to make sure each fish gets enough food throughout the day.

Be sure to remove any uneaten food from your tank after feeding time as even small amounts of leftover food can cause large issues in water conditions including increased ammonia and nitrates.

How much to feed blue green chromis?

When feeding any fish small amounts throughout the day I recommend using the 3 minute rule. This is where you give your fish as much as they will eat in a three minute timespan. Be sure to watch your fish as they eat as some might try to bully others depending on the established pecking order or hierarchy of each small school.

Common diseases of blue green chromis?

While there are no diseases that specifically target blue green chromis, you should still be on the lookout for potential illnesses. These can include marine ich, and velvet.

TIP

You might hear marine ich referred to as “crypt,” this is because the protozoan parasite that causes this disease is named Cryptocaryon.

Regardless, to avoid any diseases you should be sure that your community tank stays clean and maintain proper water parameters within the tank.

Blue green chromis lifespan

When well taken care of this species can live in captivity for 8 to 15 years.

Breeding

Breeding the blue green chromis can be difficult and is often compared to clownfish breeding.

Can you breed a blue green chromis?

While it is possible to breed this species in captivity it is very difficult, and is impossible if they perceive any of their tank mates as being a threat.

The optimal spawning range is between 79 and 83 degrees Celsius.

TIP

Bristle stars, crabs, and wrasses will eat the eggs of your chromis if left in your aquarium. It is best to carry out the whole process in a separate nursery tank.

How to breed a blue green chromis?

When preparing to spawn the male chromis will be more territorial and aggressive, and will often turn a pale yellow color.

The male will initiate the mating process by building a nest in the substrate and then going and finding a female. If the female is ready she will follow the male back to his nest and lay her eggs. Males will often repeat this process with several females.

Males are very protective of their young and will guard the eggs until they hatch, fanning them with his fins. You might see him eat a few eggs but rest assured that they are likely dead or diseased.

Chromis eggs hatch in two to three days, but they are extremely fragile fry. They will feed off of the eggs yolk for the first 48 hours, after which you can begin feeding them infusoria and other foods when appropriate.

Is the blue green chromis for you?

If you’re looking for a low maintenance and easy going fish that will get along well with others, then this fish is probably for you!

Conclusion

The blue green chromis is an excellent tropical fish for beginners. With a water heater, a 30 gallon tank, and rudimentary care for your fish, this fish is sure to add a pop of color to your saltwater tank!

Featured Image – Philippe Bourjon, CC BY-SA 4.0, via Wikimedia Commons
(1) Rickard Zerpe, CC BY 2.0, via Wikimedia Commons

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