Found this in my tank some time ago, but didn't think it was alive. However, today when I was cleaning the glass saw it close up and then open a few minutes later. So that brings me to my question. I know that people keep clams, but am not sure that this Mussel? thing is something that may somehow cause problems. It has been in the tank for 6 plus months, and hasn't caused any problem, I'm aware of, but I am not knowledgeable on this subject and was hoping for some additional information. Thanks in advance for any info