Some may run it 24 hrs a day but I would not. When I first got it I ran it 24 hrs a day it it dropped my nutrients fast. That light is very effective at growing algae. There was a point when I ran it 3hrs at night because it worked too well but I think I’m at 10-12hrs now.I’m looking now for my fuge light now for my new system. This could work great. How many hours a day do you run this. In my current system I run my fuge light 24/7. Not sure I would be comfortable running this all the time [emoji91] [emoji91] [emoji91].