rack temps

to clarify, it doesnt have back heat, i said it has heat tape running along the back of each shelf, meaning the tape is on the shelves and towards the back of each shelf. and i have stabilized the temps by using some blankets. i would try the the empty tub method but i dont have any empty tub to use. its a small rack with only 3 shelves and all 3 are occupied. thanks for all the replies and sorry for the confusion

Back heat, heats the air. While the belly heat tends to put the heat more where you want it. Giving them a hot spot and then the heat spreads out in the tub before excaping into the room. Then the front of the cage you have a cooler spot. I have both and I prefer the belly heat.