On that small zoa tank that you saw in my living room the other day, I have a powerbright unit with four bright blue LEDs. I usually run those lights from around 6:00 to 10:00 pm. On the few occasions that I've forgotten to turn it off before bed, the zoas have stayed open all night and I've noticed increased algae growth on the glass. So the tank doesn't get the benefits of night, whatever they may be.