Because crustaceans have an exoskeleton, they can not grow the same way as fish do. They must shed this outer hard shell and grow a new one. This process is called molting. The molt is called ecdysis and is the same as the one experienced by terrestrial insects. When the time comes, usually at night, the shrimp finds a safe, secluded place on the reef and begins its transformation. A little trap door pops open on its back and the animal pulls itself out of its shell. Once free, it is vulnerable for several days until it's new shell hardens. The discarded shell looks like a dead animal, in my opinion, a molting shrimp is a happy, well-fed shrimp.