Thanks everyone. It does evaporate some, and I get some condensation on the water pipe that runs across the ceiling, but it is generally not a problem. I havent had anything get waterlogged or anything like htat. Not as hard to heat as I thought it would be either. I run about 700 watts of heating to keep it at about 78.
Dimensions are 8 feet by 8 feet by 2.5 feet deep. Comes out to about 1100 gallons.
I use a filter I built myself from plans I found on the Internet. The pump is 900 gph, and the rest I built from two rubbermaid bins and some PVC pipe, quilt batting, and gravel. It has kept the water parameters in a respectable range for about 9 months now (with only one cleaning). I still have not lost a single fish out of this tank due to disease. I think the large size keeps things stable.