Hopefully it is good algae. I usually keep the lights out since I have no corals. However, for about two weeks I would keep the blue lights on. I am using RO water. The green algae is hard not soft or slimy. I have a video and photo which is the best I can do. Ammonia, nitrites, and nitrates are zero. According to my API test kit the phosphate is .25 I think. Yes I know I have to get the nitrates up and the phosphates down before adding corals. Just concerned about this algae. Thanks all