I haven't tried 6 hours of light, but 8 hours works fine. Algae aren't going to know that you intend the "display" lights only for appearance sake. They will just assume it is for their benefit and thank you by giving you some vigorous growth. Joking aside, I know some people use actinic lights for the appearance, even though they are not good plant lights. I don't like that particular appearance, but if you do, that is an option. I don't know of any other lights that would not benefit the plants and algae.