Pinched mantle is a serious issue for Tridacnids, often leading to the deaths of countless clams and causing hobbyists to pull their hair out. The symptoms include a retracted mantle that may appear “pinched” in some areas. PM, as it is abbreviated, is only known to affect Tridacna maxima and T. crocea clams and will lead to certain death if it is not treated. Fortunately, the best known treatment for PM is simple, consisting of only a freshwater dip of the clam. To perform this dip, place the affected clam in a container of freshwater and move it around to get water into its tissues. You can let the clam sit in this water for up to a half hour, and the treatment may need to be repeated in order to fully rid the clam of the parasite causing the issue. Be careful with this sort of dip, as pH differences and losing track of time can really harm your clam, most likely killing it.