Clam troubles

[The Grizz]

Then how do you explain how a perfectly healthy clam in the morning and for the last 6 month in my tank and how ever long in Dougs tank can be dead in less then 8 hrs? I have been checking all my clams an hr after the lights go out for creepy crawlies and last night there were 2 BRISTLE worms going for the bottom of my 2 biggest clams, not to mention NEITHER are on the sand bed. I got to all 4 of them before they could get into the clam but still one died. And again I said WTF!!