The Lettuce Coral is one of the most common species of coral. This coral is found in most reef habitats, from mangrove areas and back reefs all the way out to the outer reef and wall. It’s formed by groups, known as colonies, of large, thick plates which may grow over three feet across , typically in a grey, brown, green or with purple tinges in color. There are four different forms of Lettuce Coral colonies: hemispherical or encrusting, thick flat leaf-like plates with valleys and ridges, thick leaf-like flat plates without valleys and ridges, and lobes. They have high walls that are several inches tall. The colonies are developed from many small anemone type polyps. Each polyp has long tubular tentacles that are spaced wide apart around a central mouth. The tentacles are rarely extended and only at night.