I'm not sure if it's important, but when I originally got my moonlights....two, four foot IceCap lights....they were fairly bright. Here's a picture I pinched from @revhtree post from 2010....
The plan was to use them so that I could still view my tank in the evening, but what I noticed was that the fish weren't going "to bed." It might have been because of the brightness, but I now use these as part of my early morning and late evening before lights go out.