so most, use a uth with insulation on top? and this is usually sufficiant to raise the ambient temp above 80? I have a 20 g long, and using the zoomed 10-20 uth, it seems kind of small, but does heat up the glass on top pretty good, i have it plugged into a dimmer, and keep the dimmer on low, if not, then the glass jumps up to 100 degrees, which i imagine is too hot