Found this to be promising, Maybe I should give it a try? What do I have to lose?
Treatment: fresh water dips
Place the clam in RO water that the temperature is the same as your tank and (ideally) adjust the pH to match that of the aquarium. Move the clam from side to side in the water, and this will help get some of the RO water in between the mantle and shell where the parasite seems to be present.


A specimen of Tridacna maxima 48 hours after an RO dip; © Clams Direct
Try to place you fresh water dip container under some lights to encourage the clam to open a little. Take a turkey baster and shoot water at wherever the pinch it. You can leave the clam in there for 20-30 minutes. Tridacna crocea may be exposed to even longer periods of immersion, as we found that they tolerate RO dips better than T. maxima. The clam can then be returned to the aquarium.
You may find that this process will have to be repeated several times, but we would suggest waiting a day or so between dips so that the clam can recover from the process.
Other things to consider
The protozoan can be dormant when the clam is happy and healthy, only for signs of Pinched Mantle Syndrome becoming visible when the clam is stressed. Stress can be triggered by many things, including shipping, poor acclimation, poor water quality, the wrong lighting, and bad choices of tankmates.