Blue Green Chromis

The Blue Green Chromis (Chromis viridis) is a small damselfish in the family Pomacentridae, abundant on coral reefs throughout the Indo-Pacific from the Red Sea to the central Pacific. It is best known for forming large, dense schools that hover just above branching Acropora coral formations, retreating instantly into the coral's branches when threatened. Its shimmering pale blue-green body makes it one of the most visually striking and photographed small reef fish, often seen in huge numbers creating a moving cloud above the reef. The species is closely tied to live branching coral for shelter, making it a useful indicator of healthy coral cover on Indo-Pacific reefs.

The Blue Green Chromis is a small, slender fish easily recognized by its shimmering coloration and schooling habit.

• Iridescent pale blue-green to green body, often appearing almost translucent in bright light
• Forked tail fin with slightly elongated upper and lower lobes
• Translucent to pale fins with faint dark scale edging
• Large eyes relative to body size
• Lacks the bold bars or spots seen in many other damselfish
• Grows to only about 6-8 cm Its small size, uniform shimmering color, and habit of forming large schools directly above branching coral distinguish it from similarly shaped but more solitary or differently patterned damselfish species.

Blue Green Chromis are found on coral reefs throughout the Indo-Pacific, from the Red Sea and East Africa across Southeast Asia and Australia to the central Pacific islands. They are closely associated with branching coral formations, particularly Acropora species, which provide shelter from predators. The species typically occupies shallow reef flats and slopes from about 1 to 12 meters deep, where currents deliver a steady supply of plankton. Large schools are usually found hovering just above the coral canopy in areas with good water flow.

Blue Green Chromis are highly social, forming large schools of dozens to hundreds of individuals that feed together in the water column just above branching coral. When threatened by a predator, the entire school retreats almost instantly into the safety of the coral branches below. They feed primarily on drifting zooplankton, picking prey items from the current as they hover in place. During spawning, males develop a darker coloration and establish small nesting territories within the coral, attracting females to deposit eggs that the male then guards and fans until hatching. Their dependence on live coral links their abundance closely to overall reef health.