Characters: Colonies are laminar or subarborescent, with these different growth-forms characteristically occurring together in large colonies. However, colonies may be composed only of plates or, in shallow water, primarily of branches. Valleys are short, straight, and spread in a fan before dividing. They radiate from the colony centre on flat surfaces, but are highly contorted on branches. Flat surfaces often have concentric growth lines. Tentacles are usually extended only at night. Colour: A variety of pale colours, usually blue (which may photograph pink) or pale brown. Similar species: Merulina scabricula. Habitat: A wide variety of reef environments, especially lagoons. Abundance: Usually common, rare in the Red Sea.