I used to buy from both of those places before I got sakes and did some research, as its the only local source without breeding your own. My petmart sells the boxed arctic mice, and my petco sells some kind in a bag that ate a real terrible quality that the guts fall out half the time and my snakes won't touch. I recommend the boxed arctic mice more they seem to be alot better. As for the heat I'd recommend a uth as well as the light, just keep an eye on that humidity.