Can you take a Gatorade bottle and cut it in half and fill it full of 1/4" holes for water circulation and then place it over the clam to shield it. I bet it's ether your shrimp irritating it, or it looks to be a French Polynesian Maxima and I've seen lots of them not do well in the home aquarium and die after a short period of time.
Shrimp really doesn't mess with it to much. At least the mantle. But yeah sure I'll try that out! Thanks for advice! Will i be able to uncover it sooner or later or does one or the other need to go?