I've been thinking about posting an update. I was just trying to come to terms with it emotionally first. :(

It didn't end well. I knew that was highly likely but I still had to try.

When I searched for similar cases, I found only a few. And none of them had posted any positive results. (They hadn't posted negative results either, so I held out hope.)

The clam did remarkably well for about a month. It had the mantle extended normally and would still retract on its own. I always thought clams would decline quickly with some obvious signs, so I thought this was going well.

There was never any new hinge growth. After a while, the clam wasn't able to close fully - its first sign of weakness. It still tried to feed and never showed signs of pinched mantle. (Interesting.) It just slowly became weaker. The mantle wasn't even receeding.

But then... I saw nassarius snails swarming around it, so I knew it was going downhill despite it's normal looking appearance. When I returned to the house, the clam was no longer able to close at all and had its mantle pulled in.

It was hard to pull it from the tank. I felt bad knowing it was still alive, but I knew it wouldn't survive and didn't want to risk my whole tank. I'm still coping with the guilt.