The lights are not on a thermostat, I kind of just turn them on when I'm not home and the lights are on, or if the tank is a little cool I can shut them off and it will help bring the tank temp up. Also I have them wired into a selectable voltage power supply so I can crank them at 12V, but I can also slow them way down by dropping to 3.5V. At about 6V it will maintain the tank temp. at a constant when the lights are on. Beware though the evap goes up a significant amount when they are on. Thank you for watching, this tank wouldn't exist if it wasn't for everyone here at 3Reef! _________ 72G Bowfront, Mag 7 Return, Euro Reef RS-80 Skimmer, Reef Geek Retro T5HO 48"x4, Exhaust Fans, 2 Koralia 4's, 20G Sump Modified, 80 lbs. LR, 2" CC Bed, Scopas Tang, 2 Clowns, Green Brittle, Frogspawn, Galaxea, Zoa's, Mushrooms, Star Polyps, Acans, Candy Cane, and a baby Hammer  |