Green Chromis (Chromis viridis)

 

These are plankton-feeding members of the damselfish family from the Indo-Pacific region. Several very similar species also occur on coral reefs in the Caribbean and Florida Keys. Except for breeding individuals guarding clutches of eggs, green chromis typically live in schools in the vicinity of branching stony corals. They hover over the corals and feed on small planktonic creatures that drift past, quickly retreating into the protection of the coral branches at the first sign of danger.

Relatives of green chromis:

There are also numerous other species of damselfish that live in coral reef areas around the world. While some of these are also schooling plankon feeders (e.g., the striped seargeant majors so often seen schooling at coral reefs), many others are very pugnaceous fish that defend feeding and breeding territories against threats both large and small. Many of these territorial damselfish maintain algae farms on a patch of reef by clearing the patch of any live corals, by selectively removing inappropriate algal species, and by driving off herbivorous fish such as tangs and other surgeonfish. These damsels feed on the algae and/or the small invertebrates that live among the algae.

Also included in the damselfish family are the clownfish of the Indo-Pacific region. Clownfish typically live in pairs, and in the wild are always found living among the tentacles of a stinging sea anemone (clownfish are immune to the stings). The clownfish gain protection from larger predaceous fish that avoid the stinging tentacles, while the anemone is protected from anemone-eating butterfly fish, which are driven off by the territorial clownfish.