Blue-Green Chromis: A Great Species for Your Marine Aquarium

The Blue-Green Chromis is a beautiful and peaceful fish perfect for any marine aquarium.

Blue-Green Chromis – Quick Facts

In a rush? Check out the quick facts about Blue-Green Chromis below.

Fish Info

Scientific NameChromis viridis
Common Namesblue-green chromis, blue-green reef chromis, green chromis, green reef chromis, blue-green damselfish
AppearanceLight blue dorsal with a pale green belly.
DifficultyBlue-green chromis care is quite easy, as this species is considered to be one of the lowest maintenance saltwater fish around.
DistributionThe Blue-Green Chromis fish is found in tropical waters of the Pacific Ocean, east of the Philippines, New Guinea, and eastern Australia. Blue-Green Chromis live in coral reef areas and lagoons, where they prefer to group into a school.
LifespanThe lifespan of blue-green chromis is 5-12 years.
ShoalingYes, the blue-green chromis is a shoaling fish.
TemperamentThe blue-green chromis is a peaceful fish that prefers to stay out of skirmishes.
Keep in Groups of6 or more.
Tank MatesCoral, Tangs, and other peaceful saltwater fish
Dietblue-green chromis have a diet that consists of both meaty and plant foods.
Length4 inches.
Sexual DimorphismSexual dimorphism is present but not obvious. The males turn a yellow color during the spawning period.
Breeding DifficultyThe difficulty of breeding blue-green chromis might be because they need just the right conditions and safety for their eggs and fry.

Water/Tank Recommendations

Water TypeSaltwater
Water TemperatureThe ideal water temperature for blue-green chromis is 22-26°C (72-78°F).
Water pHThe ideal water pH for blue-green chromis is 8.1-8.4.
Water HardnessThe ideal water hardness for blue-green chromis is 8 to 12 dH.
Tank size30 gallons is the minimum tank size, and a larger tank is recommended.


The blue-green chromis is a beautiful saltwater fish that’s been a staple in the aquarium community for years. With their bright colors and large size, they make an impact wherever they go!

These are also very easy to care for. Even though this species isn’t considered low-maintenance by any means, their ease of care makes them a great choice for beginners (or anyone who doesn’t want to spend hours on tank maintenance).

But what if you don’t know much about them? You might be surprised how many owners there are out there with little knowledge beyond “they look pretty.” This guide will provide everything you should know about blue-green chromis so you can decide if owning one is right for you.

About Blue-Green Chromis

Blue-green chromis is a species of fish that you’ll see in many saltwater tanks all over the world. These vibrant and active fish make an excellent addition to any tank, but they do have some specific needs that need to be met.

Also known as blue-green damselfish or reef chromis, these fish can be found throughout the Pacific Ocean near New Guinea and eastern Australia. They inhabit coral reefs and lagoons, where they prefer to group into schools of six or more.

These schooling habits create a very dynamic view for viewers in your aquarium! However, it is important not to keep them with aggressive species since others will often pick them on when left alone.


The body of the blue-green chromis is light blue-green color. In addition, this species has a rather large and rounded head that begins to taper down towards its rear.

The dorsal fin starts roughly in the middle of their body, stretching back to about three-fourths of the way along their length. The rays of the dorsal fin are quite short when compared to other fish.

Their Length

The average length of a blue-green chromis is 4 inches.

This means you won’t need a massive tank to keep this species happy and healthy. Four inches isn’t very large, especially when compared to the more popular saltwater fish out there.

Note: The size of this fish can be influenced by a number of factors. Water quality and diet are two big ones.

If you want to make sure that your fish reach their maximum size, you need to be committed to the quality of their care.


The average lifespan of the blue-green chromis is 5-12 years.

This means that if you keep these fish in a well-maintained aquarium, they can live quite a while!

The lifespan can be drastically shortened if these fish are kept in an aquarium that is not maintained or has poor water quality.

In these situations, the blue-green chromis can suffer from a variety of diseases and live far shorter lives.

Note: Some aquarists have reported that their blue-green chromis has lived even longer in captivity. This is quite uncommon, though.

Sexual Dimorphism

There are very few visual differences between the male and female. The most reliable way to tell if your blue-green chromis is male or female is to wait until breeding season; during this time, males will turn a yellowish color.


Blue-green chromis are found in coral reefs and lagoons. They tend to stay in large groups, which is why it’s recommended that you keep them in a larger tank with other fish of the same species.

These fish will spend their days swimming around, looking for small pieces of food here and there. These aren’t large eating machines like some other species out there!

They also have algae-eating tendencies when they find it on hard surfaces such as rockwork or driftwood.

Caring for Blue-Green Chromis

Blue-Green Chromis are the kind of fish that you can just set up a tank for and not worry too much about. They’re rather hardy, they won’t damage coral or other critters in your aquarium, and they don’t require any specialized care to thrive.

However, it never hurts to know more! If you have an affinity for this species, then we recommend taking things a step further by learning as much as possible. Knowing how best to keep them happy will only enhance their quality of life.


The blue-green chromis is an opportunistic omnivore that can thrive on a large range of foods. However, they do particularly well with meaty meals like brine shrimp, bloodworms, and other live or frozen foods.

You should also supplement their diet with algae-based pellets and vegetables to ensure they get all the vitamins and nutrients they need. We recommend zucchini and spinach as favorites!

Be careful not to overfeed your blue-green chromis. These fish can be prone to obesity, so a good rule of thumb is to feed them only what they can finish in a couple of minutes.

How Often & How Much to Feed Them

Feeding blue-green chromis is a pretty straightforward process. These fish are omnivores and will eat just about anything you provide them with!

Aim to feed your blue-green chromis two times a day.

Possible Diseases

The good news is that the blue-green chromis is not especially prone to any kind of disease. The bad news is, they’re still preyed upon by some very common illnesses!

The most prevalent affliction these fish suffer from is ich. This parasitic condition can quickly spread throughout your tank, making it essential to quarantine new fish before adding them to your current community. Ich may be difficult to detect, but you might notice white spots forming on your fish’s body. If left untreated for too long, this illness could prove fatal for your entire tank (it causes stress and loss of appetite).

Luckily, there are several ways to treat and prevent diseases in saltwater tanks.

Tank Setup

If you want your blue-green chromis to thrive, it’s important to create an environment that mimics their natural habitat.

The most important thing is to include plenty of live rock. This will serve as a hiding place and enrichment for the fish, who like close proximity to other life in the tank. It also makes them feel more comfortable than tanks without any decor!

Blue-Green Chromis prefer moderate lighting conditions and warm water temperatures, which is ideal for coral growth. Having some low-lying soft corals such as mushroom or brain coral is always beneficial because these creatures love to make homes there when hungry or tired enough to need rest.

Aquarium Size

The minimum recommended tank size for a school of blue-green chromis is 30 gallons. However, a larger aquarium is definitely preferred since this species is highly social and likes to move together as a group.

It’s always better to go with a larger tank if you have the room.

Going smaller than 30 gallons can cause stress and fighting among the fish due to overcrowding.

Water Conditions

The most important thing to consider when setting up the water conditions for your blue-green chromis is its natural habitat. In their native waters, these fish live in sheltered lagoons and shallow reefs that are protected from waves and other storms.

Blue-green chromis prefer temperatures between 72°F and 78°F, a pH level of 8.1 to 8.4, and hardness levels that range from 8 to 12 dH.

The water should be relatively clean, with a moderate current.

It’s important to perform weekly water changes of about 25 percent to keep your aquarium in good shape. Check the parameters regularly and make any necessary adjustments as needed.


The pH balance of the water is a very important factor to consider when caring for your blue-green chromis. The recommended range is 8.1-8.4, so it’s on the higher end of the spectrum (which means you should be vigilant about monitoring it).

Note: Some aquarists have gotten away with slightly different levels by utilizing specific filtration methods and additives in their tank. However, we don’t recommend this as it can compromise their health.


The ideal water temperature for blue-green chromis is 22-26°C (72-78°F). This should be right in the middle of the recommended range, but you’ll want to make sure that you check this regularly.

If your tank doesn’t have a heater, you might need to adjust its water temperature accordingly. A drop by just 2 degrees can cause serious health issues, so take care of this ASAP.


The recommended hardness level for blue-green chromis is 8 to 12 dH.

Most commercially available saltwater fish can do quite well in waters with a range of between 8-12 degrees of hardness, so this should be an easy requirement to meet as long as you’re using quality tank and water conditions.

This is one of the reasons why blue-green chromis care is so easy. You can use mostly common tank recommendations and know your fish will likely be fine.


Having a strong filtration system is essential for keeping blue-green chromis healthy. When choosing an aquarium filter, you should look for one with moderate flow and medium-sized media compartments.

There have been reports of these fish becoming ill from poor water quality, so be sure to perform regular water changes every week or two. About 25 percent of the tank’s volume should be changed each time.

Aquarium Plants

Planting live plants in your tank is always recommended. Not only do they help improve the health of your fish, but they also provide a unique look to your aquarium!

When it comes to blue-green chromis and planted tanks, you have some options. However, these fish are quite active swimmers who love exploring their environment. As a result, many plants tend to get uprooted or destroyed by this species.

If you want to incorporate plant life into your tank (and don’t mind having them trampled), here are a few types that can be included:

  • Anubias Barteri – This popular freshwater aquatic plant grows well in shady areas with moderate light exposure.
  • Floating plants such as Hornwort or Java Moss.

Behavior and Compatibility

As mentioned earlier, the blue-green chromis is an easygoing fish. However, they may pick on small tank mates that are slow-moving or long-finned.

This species can be very active and will spend most of its time swimming around the aquarium in a school. They prefer to stay close together for safety when scared by other creatures outside their environment (particularly if you have predators, which we don’t recommend with this species).

They’re also known to get along well with certain kinds of marine life. This includes cardinalfish, tangs, wrasses, and clownfish! Do note that aggressive tank mates will cause problems for this peaceful shoaling fish.

How Many to Keep Together

The recommended number of blue-green chromis fish you should keep together is six or more. If you have a larger aquarium, 12 or more can be kept together.

Remember that these are schooling fish and will stick close to each other for safety when confronted with danger. When kept in groups, they’re also much happier and exhibit their natural behavior.

If you have a smaller tank, keep two or three fish together. However, be sure to provide enough space for each fish to swim and get exercise.


The Blue-Green Chromis is a peaceful fish that gets along with others. They can be kept in groups of six or more.

Aggression isn’t an issue as long as you keep them in a large group and provide adequate space for everyone to get comfortable.

Tank Mates

The best tank mates for blue-green chromis are other blue-green chromis. These fish naturally school and do well with others of their kind.

You only need to give a large enough environment for them all to swim together in one group (roughly 6-7). Too many blue-green chromis could lead to squabbles, so it’s important that you keep the numbers appropriate for the tank size.

Beyond other blue-green chromis, the fish is compatible with the following:

  • Cardinal Tetra
  • Apistogramma species


Breeding blue-green chromis is possible and doesn’t require much extra work. However, you will need to set up the breeding tank right if you want the process to go smoothly.

The first thing to do is separate a pair or two from the general shoal (depending on how large your main tank is). You can use a net and move them into another part of the aquarium temporarily until you’re ready for breeding.

As a shoaling fish, they will do most of the work themselves. The females lay eggs in the substrate of your tank, and the male will fertilize them. Don’t worry if you see the male eating some eggs; he only eats the ones that don’t hatch!

After 2 or 3 days, the eggs will hatch and the male will leave. To avoid having the fry preyed upon, we recommend moving them into a separate tank and feeding them until they are big enough to be introduced into the main aquarium (usually after about 50 days).

Are Blue-Green Chromis Fish a Good Choice For Your Tank?

Blue-green chromis are a perfect choice for anyone who’s thinking of starting an aquarium.

We recommend this species to beginners all the time because they’re so low maintenance and simple to care for. Once you get comfortable with their basic requirements, it won’t be long before you start paying attention to other saltwater fish!

This is why we feel confident in saying that if you stick with them early on, there will come a day when you look back and wonder what took you so long.


The blue-green chromis is a very hardy and low-maintenance saltwater fish. They’re also quite pretty to look at, which makes them an excellent addition to any tank.

It’s not just their looks that make them desirable, though; the way they behave in your aquarium can be quite charming as well! These fish are fun to observe because they love swimming together in a school (or shoal). You might see several of these colorful fish gallivanting around your tank throughout the day!


The only true downside to blue-green chromis is the potential for aggression. Although it is rare, they can be territorial and may bully or attack other fish that are smaller than them.

When you add this species to your tank, it’s important to consider how they might interact with peaceful fish of comparable size. It’s also worth noting that these aren’t considered good choices for nano tanks (small aquariums).

Note: These fish aren’t ideal for nano tanks because they could potentially become aggressive in a tank that’s too small. They also require larger tanks to stay healthy, which goes against the concept of a nano tank setup.


Blue-green chromis are a fantastic species for your saltwater tank. Whether you’re an experienced aquarist or someone who wants something easy, this is the fish for you!

Their low-maintenance nature and beautiful look make them one of our favorite fish to recommend. If there are any other questions about these fish that we didn’t cover in this guide, feel free to send us a message.

We’re always happy to help!

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