There is a bulge on this astrea snail that looks to be attached pretty solid if not part of the shell. My question is what’s living inside? I see a worm like appendage sticking in and out with a line of mucus like material strung out of it. Should I do something or let it be?
Vermatid Snail. If not already present in the tank you could super glue the opening to kill it. Otherwise if the system already has vermatid snails then just leave it.