My 40G evaps close to 5G a day when its this hot.
I picked up an Auto-Top-Off off of AB Aquatics. It works great and best of all its only $50 tax in. Add an old powerhead and a small length of tubing (everyone has these lying around) and an empty 5G salt pail and you are good to go. You still have to top off the bucket everyday but the tank level and params are more stable this way.
http://www.abaquatics.com/