Good to know. I thought about building one as well, but, didn't notice any temp spikes in the summer, (the tank is in the coolest room in the house), BUT, I was not running MH bulbs either, (will be running 3 - 4, 400 watt ones this summer... but, the tank will be much bigger, so, we'll see if I'm going to have to buy a chiller this summer
).
Robert