The Green Chromis is an iridescent blue-green damselfish that schools in the open water of a reef.
Hardy, inexpensive, and active, it adds constant movement, and unlike most damsels it is relatively peaceful, which makes it a reasonable beginner shoaling species.
They are among the tougher marine fish available and tolerate minor beginner mistakes within a cycled tank.
A well-fed group moving in unison across the tank is a striking display.
Housing
Keep a group in a cycled tank of 110L (30 gal) minimum, with larger volumes strongly preferred so the school has swimming room.
Maintain salinity 1.024-1.026, temperature 24-27°C (75-80°F), pH 8.1-8.4, and nitrate low, with the moderate-to-strong flow they prefer.
Provide open swimming space plus live rock for refuge.
A larger tank and bigger group help spread out the aggression that develops as they mature and keep the schooling behaviour intact over the long term.
Diet
Green Chromis are omnivores.
Offer a marine flake or pellet staple plus frozen mysis and brine shrimp, fed once or twice daily.
In the wild they pick zooplankton from the water column, so they appreciate small foods that drift in the current.
They feed eagerly and rarely need coaxing, which makes them easy to keep well-fed in a busy tank.
A varied diet maintains their blue-green sheen and supports the group's condition and activity.
Health
Chromis are hardy and disease-resistant, tolerating minor parameter swings better than most marine fish.
The main issue is stress-driven aggression within the group, which can lead to injuries, bacterial infections, and a dwindling school.
Quarantine new fish and keep nitrate low; marine ich is the usual risk after poor quarantine.
Watch for nipped fins and isolated, hiding individuals as signs of in-group bullying.
A large enough group and tank keeps stress and disease low.
Temperament
Peaceful by damselfish standards and reef-safe, Green Chromis school together in open water and ignore corals.
However, as they mature a hierarchy forms and dominant fish often pick off subordinates one by one until only one or two remain.
Counter this by stocking an odd-numbered group of five or more at once in a roomy tank.
They mix well with other peaceful community fish and add coordinated open-water movement.
Beginner
Beginner
Beginner
Beginner
Beginner
Beginner