I agree with the use of fan(s). I have used fan(s) extensively on different tanks over the last 20 years.
Evaporative cooling is not only the simplest but the most cost effective way to cool a tank. The temperature can be dropped by 10 degrees or more, even for a hot tank in a hot room. The angle of the fan at the water determines the cooling productivity. The fan can be placed on the same timer as the lights or a separate timer. Of course a controller can control a fan based on exact temperature settings.
Reducing the lighting also reduces heat. I would also consider just using the blue lights. That's the spectrum of light that coral most need and will keep them alive during the light reduction.
To make sure the heater is not trying to keep a minimum temperature and defeating the cooling effect of evaporation, unplug it. A swing from 70 degrees in the morning to 80 by evening is not harmful, as long as the temperature does not go over about 82. Allowing it to go near 70 lets the temp rise 10 degrees without causing problems.
Now let's talk about top-off for evaporation. A really easy way to do this is the drip method. Using an air valve meant for air bubblers, or simply tie a knot in the line, drip the water from a 5 gal bucket on a chair or ladder. Setting the drip rate can be set pretty easily in less than an hour by watching the level and adjusting accordingly.
A fancier method of top-off is what I call the Glug Jug. It's a fail safe method that I can explain if requested.
That's my 2 cents.
Aloha,
Mark
808-345-1049
Edited by Mark Peterson - August 03 2013 at 8:00pm