Evaporation could be big too, every gallon translates to about 2400watts of power being pulled out of your tank (the key is how quickly that occurs!). However the rate at which evaporation occurs is quicker when there's a larger gradient in temperature (translation: the colder it is the faster your water will evaporate), so you might be very well off to completely cover your sump, frag tank, fuge, as much as possible since those are in your basement. You'll create a humid barrier of warmth that lowers the overall rate of evaporation, you can still leave your display tank uncovered though (although your canopy most likely provides some level of cover as well.