Acropora

Acropora is one of the largest groups of corals. They are all characterised by an axial corallite. The growth form is usually branching, but can form both flat plates and plates with short branches growing up from the plates.
Many species are the fastest growing corals, but have fragile skeletons easily damaged by ships anchors and storms. Viruses have decimated populations in the Caribbean.
The structure of many species makes them a perfect shelter for many species of fish and crab. At the first sign of danger, young fish hide between the sharp branches. Larger fish make their home below platelike colonies. This makes Acropora an important contributor to reef biodiversity.






























Galaxia

Galaxia is a relatively easily recognized by it's high protruding septae. It can be encrusting, massive or branched.
Colonies with deep troughs between the corallites together with high corallites are often hosts to a unique species of pipefish. Another form of symbiosis that enriches the species diversity of reefs.







Montipora

Montipora is a very varied genus as can be seen in the images. The corallites are always small and set between skeletal structures. When branched the branch ends are usually fluted.












Porites

Porites corals all have tiny corallites, under 1.5mm in diameter. In contrast to Montipora, the corellites have well developed walls. They can be branching, or truly massive colonies looking like huge pale brown boulders.
Parrotfish graze on reef corals as cows graze on grass. The damage you see on one of the Porites images was caused by a herd of large Bumphead Parrotfish. The white sand beaches so popular in many areas of the tropics are produced by Parrotfish. An adult Bumphead can produce 90kg sand a year.











