Very Sad Story, My Tahitian Maxima clam suffered what many hobbyists refer to as “Pinched Mantle” syndrom. The “pinched mantle” is caused by a protozoa infection, similar to that of the malaria type for human infection. This type of infection is widely spread amongst Maxima and Crocea clams, and has recently spread towards other Tridacna clams such as Derasa and Squamosa.
After doing lots of research, I decided to perform the freshwater dip (FD) treatment. The principle of freshwater dip is to kill invertebrates and bacteria cells by osmosis while the water finds equilibrium between brime and fresh. The Tridacna clam is actually surprisingly hardy when completely submerged under the freshwater. The key is the water must be of the same temperature and of the same pH level as the home aquarium. The photo above is my clam being soaked in freshwater for 30 minutes.
The photo above shows the pinch of the clam prior to the dip. You can see the second scute of the left mantle is slightly shrank. It is better to detect the distress and treat it while the clam is still strong and relatively healthy versus making the very invasive freshwater dip during its latter stage.