Ring cowrie (Monetaria annulus) are small marine snails feeding on algae and detritus they make an interesting addition to your tank. Cowries are able to completely cover their body with their fleshy mantle and will commonly do so when not feeling threatened, the mantle is a specialized organ that is responsible for the amazing sheen and markings of the shell, it is also responsible for repairing the shell and protecting it against any encrusting algae or coral that may otherwise try to grow there.