Fish Active during the day

Blue-green Chromis

Chromis viridis

iNaturalist Wikipedia

A shimmering jewel of the Indo-Pacific, the Blue-green Chromis brings synchronized movement and iridescent color to the world's coral reefs.

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Quick Identification

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Size

7–10 cm (2.8–4 inches) in length; weighing approximately 10–20 grams

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Colors

Iridescent apple-green to light blue; shimmering scales that shift color with the light; males may develop a yellowish tint during spawning

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Key Features

Deeply forked (V-shaped) caudal fin
Iridescent pale green or turquoise scales
Slender, oval-shaped body profile
Large, conspicuous eyes
Small, upward-pointing mouth

When You’ll See Them

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Activity pattern Active during the day

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Peak hours 8 AM - 4 PM

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Season Year-round

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Diet Primarily a planktivore that feeds on zooplankton in the water column, supplemented occasionally by filamentous algae.

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Habitat Sheltered coral reefs, shallow lagoons, and areas with dense branching coral growth.

public Geographic range

Where Does the Blue-green Chromis Live?

The Blue-green Chromis is native to the vast tropical waters of the Indo-Pacific region. Its territory stretches from the Red Sea and the eastern coast of Africa across to the Line Islands and Tuamotu Islands in the central Pacific. They are particularly abundant in the coral-rich waters surrounding Indonesia, the Philippines, and the Great Barrier Reef in Australia, though they also range as far north as southern Japan and as far south as New Caledonia. While they are a staple of the marine aquarium trade globally, there are no significant established invasive populations outside their native tropical range.

Basemap © OpenStreetMap contributors

9 Countries

55M km² Range

Least Concern Conservation

ID Indonesia PH Philippines AU Australia Fiji Maldives

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iNaturalist / Verified observation data

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Behavior

The Blue-green Chromis is a highly social species known for its tight-knit schooling behavior. In the wild, these fish are almost always found in large groups, sometimes numbering in the hundreds, hovering just above branching corals like Acropora. When threatened, the entire school performs a synchronized retreat, diving simultaneously into the protective branches of the coral for safety.

These fish are diurnal, meaning they are active during the daylight hours and rest deep within coral crevices at night. Within the school, they maintain a loose hierarchy, though they are significantly less aggressive than most other damselfish species. Their interaction with humans is generally shy; they will maintain a safe distance from divers or cameras unless they have become accustomed to a stationary presence.

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Camera Tips

Capturing the shimmering beauty of the Blue-green Chromis requires careful consideration of underwater lighting. Because their scales are highly iridescent, direct artificial light can cause 'hot spots' or blown-out highlights in your footage. If using a reef camera, position it so that the sun is behind the lens or use a diffuser over your external lights to bring out the subtle transition between apple-green and turquoise.

To capture the most natural behavior, place your camera near a colony of branching Acropora coral. This is their 'home base.' Set the camera on a tripod or mount it to a stationary rock (avoiding live coral) and leave the area for 15-20 minutes. These fish are sensitive to movement and will only exhibit their rhythmic, hovering schooling behavior once they feel the environment is quiet and predator-free.

Frame your shot wide enough to capture the entire school rather than focusing on a single individual. The AI tracking on EverydayEarth cameras works best when it can see the group's collective movement against the static background of the reef. If you are looking for action shots, try to record during mid-day when the current is running; the fish will face into the current to catch drifting plankton, providing a dynamic 'treadmill' effect where the fish remain in the frame while swimming vigorously.

Similar Species

Species that look similar or are commonly confused with Blue-green Chromis.

Black-axil Chromis

Look for a prominent black spot at the base of the pectoral fin, which the Blue-green Chromis lacks.

Yellow-caudal Chromis

Has a similar body shape but features a distinct yellow tail and a darker blue-grey body.

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Frequently Asked Questions

Blue-green Chromis are strictly diurnal, meaning they are most active during daylight hours. They emerge from their coral shelters shortly after sunrise to feed on plankton and return to the safety of the reef crevices as the sun begins to set.

The best way to attract Blue-green Chromis is to locate healthy branching corals, such as Acropora or Pocillopora. They are naturally drawn to these structures for protection. While some use 'chum' or food to attract fish, it is better to remain still and let their natural curiosity bring them back to their favorite coral head once they realize you aren't a threat.

In their natural habitat, Blue-green Chromis are planktivores. They spend their days hovering in the water column, picking tiny zooplankton—such as copepods and larvae—out of the current as it passes over the reef.

Blue-green Chromis are strictly marine fish and are only found in saltwater reef environments. They are common in 'backyard' settings only for coastal residents living near tropical reefs or for hobbyists with home marine aquariums.

The easiest way to distinguish them is by looking at the base of the pectoral fin. The Black-axil Chromis (Chromis atripectoralis) has a distinct black spot at the base of its 'arm' fin, whereas the Blue-green Chromis (Chromis viridis) lacks this dark marking and is generally slightly smaller.

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