A lot of people have probably come to know these as a Pseudocorynactis. This genus, however, has since been found invalid. The species Pseudocorynactis caribbeorum, can now be labeled Corynactis caribbeorum. >> World Register of Marine Species <<

This small anemone can sting and can spread, but is in no way a pest like the other hitchhiking aiptasia or mojano. They are non-photosynthetic and come out at night to feed and are often extended at dusk/dawn. Leave them be and enjoy them. More than likely they will be gone in short order.