forgot, I try to keep my tank at 80, it ranges from 79-81 often, and I have seen 76-84, thats about the worst Id like to see it too.
I have 40g total volume, and I would like more volume some day, it actually fluctuates pretty fast, nanos could fry in an hour in the wrong conditions.
I have two fans, a small one in the sump, and a large desk fan like 10", is on the desk next to the tank, it turns on if the temp is above 80, so some days, it runs all day, I see up to 1/2g more evap on hot days, if my tank went up. House AC, and open top tank.
I use a 100w heater on 40g