I my window AC blowing directly on the tanks about 9' away, it seems to work. Temp is around 79deg. Keeping fingers crossed.I tried not to let my tank get any hotter than 82 in the summer. To combat this i'd either A.) Turn on the AC or B.) I have a huge box fan that i'd face into the sump to help with evaporative cooling. Could usually keep it 2 to 3 degrees cooler that way.