Hello everyone, I was recently informed that a heat pad should be used for my pacman frog's enclosure. He is in a 10 gallon tank right now. I had the thermometer at the top left corner of his cage and it was reading a constant 78-80 temperature. I've since then moved it to about an inch away from the substrate as recommended by a forum member. I was wondering if I needed a heat pad what size heat pad I needed to get. I've got one that is 3x3 from an old hermit crab cage I had when I was younger. Is that big enough to supply the cage with the proper heat? Or do I need to go bigger? The heating pads that I was looking at are these;
Adjust-A-Temp Reptile Heat Mats

What size would you guys/gals recommend I get? I'm new to this and want to provide the best possible care for my little room mate. Any light you could shed would be greatly appreciated as always. Thanks for viewing,

-Eric Buschman