Green Chromis

Green Chromis: Chromis viridis

Green Chromis Care Guide

The Chromis viridis, commonly called Green Chromis or Blue Green Chromis is one of the most popular fish species in the entire aquarium trade because of their very affordable price, great coloration, the boldness and energy they bring to the tank and the fact that they tend to shoal and are often purchased to creat that schooling effect in our tanks.

In the wild, the Green Chromis my grow up to 4 inches long, but captive specimens are usually only 3 1/2 inches. In captivity, the Green Chromis may live 8 – 15 years–although if you are purchasing several specimens, in order to watch them shoal (school), I predict the lifespan of all but one to be much shorter than that. But I’ll get more into that later.

Ideal habitat

In the wild, it would inhabit coral reef areas in the Indo – Pacific areas, and are usually found in large numbers in lower water flow regions, like lagoons. They like to swim in shallow waters, with a maximum depth of 36 inches.

Although not very large in captivity, the Green Chromis do need a large tank that provides enough swimming space. According to Live Aquaria, the minimum recommended tank size is 30 gallons. I can agree with that, in principle, because these fish are active swimmers, but they are also not that large, so 30 gallons feels a bit small but also about right.

In the wild, they like to live and hide in large coral aggregations, so a tank full of SPS corals hosting a shoal of Blue Green Chromis is a stunning display and is often what we try to create when we purchase these beautiful and relatively inexpensive (by saltwater aquarium hobby standards) fishes.
Chromis viridis 2011


These fish are planktivores, by nature, meaning they tend to eat planktonic critters like fish eggs or larva, copepods, mysid shrimp, etc.

Being planktivores, the Green Chromis is best fed several times a day (at least 3 times), as they use to feed throughout the whole day from the water column.

Behavior and tank mates

The Green Chromis is readily available in fish stores and is a peaceful fish that is thought to be generally tolerant of other Green Chromis in the tank. I have purchased 3-5 specimens at a time and placed them in my own display tanks with the hopes of creating a shoal of my own.

If you add more than one Blue Green Chromis to your tank, what you will find is that the group will form a pecking order where the dominant/aggressive fish will chase and harrass the submissive, smaller fish. In my experience, this behavior happens until the submissive fish ‘vanishes’ from the tank, most times without a trace. The aggression is then directed on the next in line and so on and so forth until that one big aggressive Green Chromis is left.

I’m not sure that’s what happens all the time, but if you search on forums, you’ll find a similar story to mine in a lot of cases.

There was an article in CORAL Magazine recently, Piscine Passels: Social fishes for the marine aquarium, by Scott W. Michael. In that article, SWM recommends you keep a minimum of SIX fishes to keep the aggression dispersed adequately, although he then is quick to suggest that groups twice that size are even more likely to thrive.

Beyond their behavior amongst the shoal, the Green Chromis is generally a community-friendly, reef safe fish.

Green Chromis

Pros and cons

All in all, I’m a big fan of the Blue Green Chromis. This relatively docile and inexpensive creature is early on the list for most people starting out in the saltwater aquarium hobby–and they make a great saltwater aquarium starter fish.


  • Inexpensive
  • Hardy
  • Can be kept in shoals
  • Active and bold behavior
  • Reef safe, they won’t attack your SPS coral, LPS coral, Zoanthids or Soft Corals


  • May carry in parasites (so use proper quarantine)
  • Will show aggression between other members of the species
  • Prone to the ‘vanishing act’


The Greeen Chromis is a lovely community fish that won’t cause any trouble in a reef tank. Do you have any in your tank? If so, leave a comment and a picture and show them off!



  1. Hi Al, I had the same experience with the green chromis I had 4 of them and they were ok for about 6 months and then started vanishing until I had just one, that is still in my tank and is fine. I found this article very interesting nice to know that it wasn’t my fault I lost them just natural behaviour

    1. Author

      Pete, thanks for the comment and sharing your experiences. I’m also glad it wasn’t ‘just me’, although I just met someone yesterday who had kept 4 green chromis in her tank for some time, with no problems…seems like maybe there’s a bit of randomness mixed in.

      However, thinking about them this much makes me want to try again…

      1. Thanks for the reply Al, maybe the lady in question still has the vanishing trick to come, I hope not

      2. Hi Al, hope you don’t mind me emailing you I have a question, I am about to get a larger aquarium and after cycling it what is the best way to change corals over from one tank to another? Or is it just trial and error? The lights on the new tank are going to be a lot more powerful than the ones I have now so what will I need to do with them to start off with? Is it worth buying a PAR meter and if so which one would you recommend ? Thanks for your time and great emails this week


        1. Author

          Pete, the goal here is to avoid shocking your corals. So you want to try and match the conditions as closely as possible and gradually introduce them to the new/future/desired state. Matching water chemistry is very important, as is matching lighting intensity. A PAR meter will help you with that. Try to start the corals out in an area of similar PAR to where they were in the old tank…and gradually move them into the spot you want, as you are able to confirm they are adjusting well.

          1. Hi Al, thanks for the information do you know of a decent PAR meter ?

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