Food for aquarium and invertebrate fish. The Copepod (Calanus finmarchicus) belongs to the family of Calanoid Copepods and, with its high content of o 3 fatty acids and proteins, it constitutes an essential energy of energy in North Atlantic. Small dried and partly dehilized crabs, of a size of approx. 2 - 3 mm, are a real delicacy for fish and a plankton substitute essential for large and small polyps corals.