I just bought an under-tank heater to increase the temps in my BP's tank and give him some more heat at night especially, so I want to use it right. My first question is, do I need a substrate, or will just having newspaper be OK? I don't want the tank to crack or anything, so that's why I'm asking. Also, has anyone here taken the "side of tank" approach? Will that be better for warming the tank? He hasn't eaten for 2 weeks and I have determined that it is almost certainly due to temps, because he is active and otherwise healthy, so I want to maximize the effectiveness of the heater.