Just wondering were you got the Clam?
You will know gaping when you see it. the mantel of the clam should extended beyond the opening and look "puffed" for lack of a better word. a gapping clam would appear to be open without restrain and the mantel would not extended in a healthy manor.
Take a look at
www.clamsdirect.com to find healthy maxima
good luck and welcome to the wonderful world of clams
J