I have a temp sensor in the cabinet to control the fan above the chiller. The chiller really doesn't run very often yet. I have my lights turned down while im cycling the tank. I have slowly started to increase the intensity of the lights. I'm suspecting when i get the light to the intensity I want, it will start heating the water and the chiller will run more. The chiller I have actually blows the air towards the cabinet door. I don't think it will be an issue for me. If your chiller blows air towards the rear, may i suggest putting a fan on the back where the air blows to keep the temp down.