I agree with the IR thermometer.
I'm a fanatic about the temps.
I have 2 digital thermometers/hygrometers (one in each side), plus I bury those crappy dial ones that came with the tank into the substate and I have one of these:

http://www.harborfreight.com/cpi/cta...emnumber=93984

It's gives accurate, fast readings...for $20