Added 2/3/14: Please note not all parrotfish eat live coral.  In fact, most are algae eaters.  The message of the video is that parrotfish are efficient bioeroders capable of turning rock into sand.  Smaller algae-eating species can be kept in reef aquariums but you may experience varying degrees of rock erosion due to algae-grazing activities depending on the parrotfish species, its size, and its personality.