Wow, Allan... I keep reading your reference to a gallon a day for evaporation loss. We use fans blowing across the surface of the water year round for temp control, with more fans during the 9 months of summer blowing across the sump. Our evaporation is about 3 - 5 gallons a day, depening on the season (5 in the summer) and we only have a little more water volume than you do. Interesting... what do you do for temp control? Do you have any temp issues?