Ok so I moved it.  I gently removed it trying not to damage its foot.  I looked at the bottom of the clam before I put it in my tank last week curious of what the foot looked like and there was nothing there.  After removing it today I looked again to see if there was any obvious damage.  What should the foot look like.  Right now it looks like several long lengths of stringy slim.  What should a healthy foot look like and a torn foot?