Staghorn corals are among the fastest growing corals on reefs, and are excellent reef-builders (2). The name Acropora literally means a porous stem or branch (3), but Acropora species express a much greater variety of growth forms than the name suggests. Colonies can resemble antlers (staghorns) and be up to two meters tall, or can form delicately engineered plates and tables that may be up to three meters across. They can also form bush-like structures, some with short non-dividing branches like the fingers of a hand (2). Staghorn corals often out-compete all other corals in shallow tropical reefs, however, their speed of growth (which can be up to 10 to 20 centimetres a year (4)) is balanced by the fragility of some of the structures, as they are easily damaged in storms allowing other coral species a chance of growth. With 368 Acropora species currently known, and with such an amazing array of shapes, sizes and colours, identifying individual species can be a tricky task (2).