OK, let me see if I understood correctly. You are having trouble with algae, so much so that you now have a layer floating on the top, right?
No, turning off the light won't affect the
live rock. If you have corals or anemones or any life that requires strong lighting, such as some clams or nudibranch, you should contact an aquarist with experience with such life forms. Other wise, you can cover the entire tank so as to not allow any light into it from outside sources. Turn of all the lights and leave it that way for three or four days. This will kill off MOST of the algae, but, not all. This will only allow you a change to clean up and search for the actual problem so you can correct it. You will want to contact Agsansoo or SGould, I can't remember which, but, one of the two are an expert in the "lights off" method.