To measure the ambient temp in tanks, just measure the unheated surface on the cool side of the enclosure
I wouldn't trade my temp gun for the world. I got mine at Crappy Tire in the auto department. Has a much further range then the radio shack one that comes in handy... it measures more than 20 feet away. My cat loves the laser too.....lol
Such an invaluable tool for herpers. That's a great price too!