What type of clam? I had two clams do fine under my pc lights. You just have to put them at the surface of the tank. Also, I disagree with you dejavu, I think you can keep most clams with t-5's, but only if you put them higher at the surface.
id say no with pc lights. expecially maximas or croceas they need way too much light. u can grow anything with t5ho than u can with mh if set up properly.(quality bulbs and ballast, individual reflectors and enough bulbs bulbs to cover the tank)