Green Chromis

The Green Chromis (Chromis viridis) is a small damselfish in the family Pomacentridae, common throughout the tropical Indo-Pacific from the Red Sea and East Africa to the central Pacific islands. It is best known for forming dense, shimmering schools that hover above branching coral colonies, particularly Acropora coral heads, which provide immediate shelter from predators. As one of the most abundant small reef fishes in its range, it plays an important role in reef food webs both as a plankton consumer and as prey for larger fish. The species is not considered at risk and remains widespread and abundant across coral reef habitats throughout the Indo-Pacific.

Green Chromis are identified by:

• Small, slender, slightly compressed body reaching 6-9 cm
• Overall iridescent pale green to blue-green sheen, brightest in sunlight
• Slightly forked tail fin, often with faint dark edges
• No bold bars, stripes, or spots, distinguishing it from many other damselfish
• Large eyes relative to head size

It can resemble other small planktivorous damselfish, but its uniform pale green-blue color without dark markings, combined with its habit of schooling densely over branching coral, helps separate it from similar species.

Green Chromis are found throughout the tropical Indo-Pacific, from the Red Sea and East Africa to the central Pacific, including the Great Barrier Reef and Micronesia. They inhabit shallow lagoon and reef flat areas at depths of 1 to 12 meters, almost always in close association with branching coral colonies such as Acropora, which serve as an immediate refuge. Large schools hover in the water column just above the coral canopy, retreating instantly into the branches when threatened. They favor calm, clear tropical water around 24-29°C and are rarely found far from live branching coral structure.

Green Chromis are highly social, forming large, dense schools sometimes numbering in the hundreds that hover above branching coral heads. This schooling behavior provides protection through numbers, with individuals retreating instantly into the coral branches when a predator approaches. They feed by picking zooplankton from the water column throughout the day, remaining close enough to shelter to dart back in quickly. Reproduction involves males preparing a nest site on the substrate, where females deposit eggs that the male then guards and fans until hatching. As highly abundant plankton feeders, they form an important link in the reef food chain, transferring energy to numerous predatory reef fish.