Pinched mantle is a symptom that shows up in Tridacnid clams, usually T. crocea and T. maxima, in which a portion of the fleshly mantle appears retracted or pinched. Being a symptom, pinched mantle is usually a sign that the clam is under attack from protozoans, like those from the Perkensis genera, or some other microscopic organism. Clams that get this symptom, if not treated properly, will quickly deteriorate and die. Fortunately, there’s a simple solution. Place the clam into a buck of reverse osmosis (RO) water, but first make sure the water is of the same temperature and pH as the water in your aquarium. Let the clam sit in the water for 20-30 minutes, making sure to gently move the clam about in the water so that the freshwater reaches all of its tissues. Then put the clam back into the aquarium, repeating this process several times over many days.