The only nocturnal thing I have in the tank that I put there on purpose is a Fighting Conch. Actually, I'm not sure if it is nocturnal, but night time is the only time I see it lol I really need to get some reference books for this hobby :S The lunar links that you are talking about are the ones I have. White, as well, in fact. Have you ever tried the blue? I have two white right now, and I was thinking of adding one blue one to angle across the whole tank and get some of color actinics give. But, I also don't want to make it too bright. It is only a 4 foot tank.