I have maintained a successful reef tank for five years with a wide variety of fish, inverts and corals. Over the past year I have bought 3 clams, two derasas and one maxima. The two derasas died within weeks of adding them to my tank and three weeks ago I purchased a maxima and it is slowly dying also. All of my corals and fish are perfectly healthy and my tank parameters are fine. I am scratching my head once again wondering why another clam is dying. Does anyone have any clues? Are there certain kind of tank parasites that could be killing them?