My system runs between 80 and 82. I have 5 250 watt MH, 14 39 watt T-5's and 2 160 watt VHO's. 3 of the 250's, 8 39 watt T-5's, and the 160 watt VHO's run during the day on the display and the other lights run at night in the fish room downstairs. Its a total of approx 550 gallons on the system. I am comfortable with the temps being at 82.