I have this clam that I got few weeks ago but it will not open up. Not sure if his happy. It is about 2+ inches. He opens a little but fish swim over him and he hides. Not sure if it the fish or water quality. This is an SPS tank so water is clean and maintained. Here is a picture let me know what you all think? I am new to clams. Second picture is a dresa, he looks okay.