Green Chromis (Chromis viridis)

The Green Chromis (Chromis viridis), also sold as the Blue Green Chromis, is a small, peaceful damselfish that flashes metallic blue-green as it hovers in open water above the rock. It is reef safe, easy to feed and a great beginner fish, and a group of them moving together is one of the classic sights in a reef tank. Build out the rest of the system with our saltwater fish and supplies.

Buying a Group? Read This First

Chromis school in the wild, but in an aquarium the group sorts out a pecking order. In a small tank the strongest fish can pick on the others until only one or two are left. Give them room (55 gallons or more for a school of five), add the whole group at the same time rather than one by one, and keep an odd number of five or more so the bullying is spread around. A single chromis or a trio does fine in a smaller reef.

Care Guide

• Tank size: Starts in a 30 gallon; plan on 55 gallons or more for a school of five or more. Leave open swimming space above the rockwork.
• Water: 72 to 78°F, specific gravity 1.020 to 1.025, pH 8.1 to 8.4. Stable water matters more than hitting an exact number.
• Diet: In the wild they pick zooplankton out of the water. Feed small meaty foods like mysis and quality marine flake two or three times a day in small amounts. Little and often keeps them colorful and cuts down on squabbling.
• Temperament: Peaceful toward other species. Any squabbling stays inside the chromis group.
• Lid: Chromis jump, especially when chased or startled at lights-out. Use a lid or mesh screen.
• Health: Hardy once settled, but like most marine fish they can catch ich and velvet when stressed. Watch new fish closely for white spots or fast breathing.

Specifications

Compatibility

Green Chromis get along with nearly every peaceful reef fish and ignore corals and invertebrates. Good tank mates we carry include the Ocellaris Clownfish, Firefish Goby, Royal Gramma, Pajama Cardinalfish and Banggai Cardinalfish.

What goes wrong: anything with a mouth big enough will eat them, so skip lionfish, groupers, larger hawkfish and triggers. Pushy fish like dottybacks and the more aggressive damsels will harass a chromis school. The biggest risk is usually the chromis themselves, so follow the group advice above.

Recommended Foods & Supplies

• Piscine Energetics PE Mysis, a top staple for small reef fish
• Hikari Bio-Pure Frozen Mysis Shrimp
• Ocean Nutrition Formula One Flake for daily feeding
• Seachem NutriDiet Marine Plus Flakes with probiotics
• Browse all fish food and nutrition

FAQ

Are Green Chromis reef safe?
Yes. They leave corals, clams, shrimp and snails alone.

How many should I keep?
One, three, or a group of five or more. Larger groups need a bigger tank (55 gallons or more) and should all go in at the same time. Adding one fish at a time to an established group usually gets the newcomer bullied.

Why did my school shrink over a few months?
That is the pecking order at work. The strongest fish chase the weakest, and in a small tank the weaker fish can't get away. More room, more rockwork and several small feedings a day all help.

Are they good for a beginner?
Yes. They are hardy, easy to feed and peaceful with other fish. Add them to a tank that has finished cycling and has stable water.

How big do they get?
About 3 to 4 inches as adults, and they reach that size slowly.

Do Green Chromis jump?
Yes. They jump when chased or startled, often right at lights-out. A lid or mesh screen prevents losing one on the floor.