Ok, thanks for all the responses! Mine was swing from 78 to 84 so I just purchased a 1/2 HP chiller. I hated to do it, but the large shop fan blowing across the water surface just wasn't cutting it. I felt the temperature swing was a bit much for the corals, and ended up losing several birds nest frags. They seem to be the only ones affected SO FAR (fingers crossed). Once the chiller gets installed, I was going to set it at 80 to start and slowly bring the temperature down to 78 over a couple weeks...