Corals are found all over the world, but reefbuilding corals are restricted to the tropics ( within 30°N and 30°S). Reefbuilding corals are generally found at shallow depths (down to 45 meters), because their zooxanthellae need sunlight.

Reefbuilding corals require warm water temperatures, and are restricted to narrow temperature ranges between 20° and 28° celcius. Reef development are generally more abundant in areas that are subjected to strong waveaction, because the waves carries food, nutrients and oxygen to the reefs, and help disperse the polyp larvae. Furthermore waveaction prevents the sedimentation of fine particles on the reefs.