Acanthastrea colonies tend to be thick encrusting or massive and can be found across all reef zones. They are generally uncommon. Underwater, the distinctive features of this genus are the tall spiky toothed septa which can be felt or seen through the thick fleshy tissue, a feature common to all members of the family Mussidae. The corallites can be rounded, angular, and sometimes elongated. Corallites are usually cerioid (common walls) but can sometimes be subplocoid (walls separated to a degree). The fleshy tissue that characterises this genus can often mask the exact nature of the corallite walls.