Ok this is a relatively simple task. There are two or three ways to heat these cages. First, you could buy several feet of THG heat tape from Reptilebasics.com. You could have individual pieces(all must be same size) wired together for each shelf resulting in only one plug or you could have one solid long piece of tape snaked from shelf to shelf top to bottom. The other option is purchase several appropriately sized UTHs(under tank heaters) and put one under each tub. There will be a plug from each one that you will plug into a grounded power strip and then plug the power strip into a single thermostat. I would look into the HERPSTAT 1. It is a very solid investment for anyone venturing into a rack system. Unless you have multiple species in the same rack requiring different levels of heat you will only need one thermostat. Hope this helps.