[pwhitby]

A chiller does not help lower evaporation....not directly at least.

Evaporation is a function of temperature and humidity. As your tank temp rises so does evaporation. So a tank at 82F evaporates more than a tank at 78F. - Thats the difference. But of course thats at a cost in electricity.

If you really want to stop evaporation, place a glass sheet over the tank, but only do this if you have a very good skimmer to ensure the water is oxygenated.

Another way is to completely enclose the hood and use a ductwork to remove the warm air....but thats rather ugly.

One other tip, reduce the splashing of the water as much as possible. This really speeds up evaporation.

But.....for every decrease in evaporation you make, the warmer your tank will become since it can not lose heat.

A dehumidifier works extremely well, but they can be quite costly to purchase and to run.

HTH
Paul.