Clams require intense lighting, so you need to figure out how much light is produced by the PCs, total. They should be marked on the base of the bulbs the wattage, add it all together and see what it comes out to. Even the most undemanding clams will need roughly 5 watts/gal of water, or in a 75, 375 watts of light. Granted, this is a rough estimate, some require more than others, and placement in teh tank is also a factor. Most clam-keepers say that MH lighting is a must, and most clams will be a much more intense color under MH than other lighting, but they have been successfully kept under PC and VHO. Feather dusters don't require any light to live, and sun polyps actually prefer dim lighting and should be placed low in the tank, preferrably under a ledge. Clams also require excellent water quality and lots of calcium in the water which you will have to add as needed, and test for, so you will need a calcium test kit. Read as much as you can on clams before you venture into keeping one, and make sure you have the proper equipment to support one, and you should be fine. HTH and good luck