[rmlevasseur]

IMO they haven't invented a heater yet that can be trusted. They are all time bombs. 75 is within limits but anything lower than that is asking for trouble. I suggest you look into a controller and temp probe. Ac Jr.'s are relatively inexpensive, and you can often find them used. I can't imagine reefing w/o my controller. For $5 I also fashioned a homemade alarm that plugs into the controller. Whenever parameters fall out of whack that alarm can wake the whole house up! Its saved me twice this year - once on temp and once on a kalk overdose.