Go with a thermostat not a rheostat. Ranco and Johnson are good yet affordable. I have 3 Vision cages and they are great. I only use them for quarrantines now because I have several rack systems. I roll up some newspaper over and under where the door is so they dont wedge themselves in that grove and then you cant get them out when you want to. I use newsaper for a substrate and it works fine. If you have a hard time getting the humidity up I tape up the metal grid/air vent(from the outside) until it holds in enough moisture