I keep an 8" fan blowing over the top of the water and lights, because the halides are HOT! My temps this summer seem to swing from 81 at night to 85 by late afternoon. I try to add some 1 lb blocks of RO ice to the tank a couple of times during the afternoon, and that seems to help, but the room the tank's in has insane temp swings from night to day (lots of windows, I have black curtains to keep the Sun out but it still cooks in there). Haven't had any fish losses since my percula went carpet surfing, and the SPS and LPS are all thriving... luckily, I guess. A chiller is just way out of my budget right now.