In addition to what was already stated, once they attach their byssal threads you can't move them. You have to move the rock they are attached to. One way to avoid this is by placing the Crocea on a half shell from another clam so it can attach to it instead. Keep in mind they are the MOST light demanding clams. They can handle and will thrive in very intense lighting. Also they have a very hard time evacuating sand from their gills, even when compared to other giant calms so be careful.