I've noticed nobody is answering. I don't have a clam but have done a lot of reading. I think people need more info to give you an idea. Are you testing your calcium levels? Clams are very dependent on calcium. Are you adding any trace elements to your water? What is his placement in the tank? What kind of lighting are you running? Any possibility of a picture? Someone may have IM you to give you help also but I couldn't just leave you hanging. Hope things are going better.

Angie