Have not seen anyone nipping but I am at work mist of the time. My female clown lives or sleeps in him. I have 3 purple tangs that I know from past experiences may bother him a bit but haven't seen it. Wrasse seems to leave him alone, as do other tangs and cardinals.
I have seen retraction in the past but it wasn't this deep or this long. I will take daily pics as I'm off for a week.
Thanks
Beautiful clam! My personal guess is that one of the tangs inadvertently nipped it, I've seen my purple come close a few times while picking around. Hopefully it recovers quickly.
For it to be pmd, the mantle would have to be retracted to the shell and a clam that big it would be pretty noticeable. You would actually see the white of the shell if it was pmd. Read this article.