Having trouble with temperature

[Guillermo]

Ok, I think there might be some hibernation going on, gonna get the undertank heater. Just want to make sure I'm getting the right thing here x:

He's in a 5 gallon tank. Would http://www.amazon.com/Reptitherm-Und.../dp/B0010OR0W6 be the proper thing or would it be too big? Or maybe http://www.amazon.com/Zoo-Med-ReptiT...er+tank+heater ?

Sorry about huge links, I cant figure out how to make links...