Take it out ASAP, and wear a mask, cuz they stink, also bring a trash can or. Zip loc bag near your tank. The cause of death was probably the fact that it was pinched mantle disease. You should do some research on that. Your clams mantle wasn’t torn it was pulling it back in reaction for protozoan. It is usually possible to cure with some freshwater dips that have adjusted ph. You can put clams into fresh water for quite a long time 15-20 minutes.Yeah, definitely a goner. Should i let it melt in the tank or pull it out? I'm wondering if there's any way to figure out the cause of death, too. It really didn't seem to do well from the week after I put it in my tank. I know they don't do well with water fluctuations, but are there any other common reasons for death? I'm gonna check it for pyramid snails, though I still don't see any. Thanks for your support everyone
Edit: I agree with the post above, what caused the PMD is hard to tell.