I have seen swings from 81 in the morning to 86 at night shut off. Sometimes depends on the outside air or humidity for me. My basement humidity fluxuates somewhat and I can see the effects on the tank temp
I run a fan on my sump when needed. I am in FL right now and my tank is in IN so I have a fan blowing on my sump via a timer so it does not run constantly. Increases evaporation though.
Definately get some fans for the canopy if you don't have any already. I have 2 fans blowing out and 1 blowing in.
*180 gal Display, 100 gal basement sump, 33 gal refugium, 3x250 MH, 2x160 VHO actinics, zoos, some softies, LPS & lots of acros and other SPS.
*100 gal prop tank plumbed into main system w/ 2x96 PC lights and 1x150 MH,