I have two tanks so chillers were out unless i wanted to get a big one and do some fancy plumbing, so i removed one of the sliders in the living room picture window and istalled a home depot $400 a/c vertical 10,000 btu unit and filled in above with plexiglass. When the house gets up above 74 i turn it on and all is fine in the tanks and me too!!! i keep mine at 78 deg., and is use two heaters in the sump, each 1/2 the recommended size for redundeze and also if one sticks i hope i find out before it does any damage.