ome species, such as T. maxima and T. crocea, prefer to be on rock surfaces high in the tanks, close to the light. Others, such as T. squamosa and T. derasa, are "sand" clams and prefer to be on a sand bed on the bottom. Some aquarists supplement feed with commercial phytoplankton cultures. Tridacna clams do filter feed on this type of plankton, but do not depend on it