The invention relates to a container assembly comprising a container fordepuration of mollusks and a drain canal unit.The assembly provides a closed circulation of water via a circulation routethat has an entry portion between the floor of the containerand the drain canal unit, a circulation channel between the corner of thecontainer and a drain canal unit, and a drain canal within thedrain canal unit. Also provided is a drain canal unit for use in stackablecontainers that provides circulation of water within a containerassembly.