Heaters are one of those things that have killed tanks. This is how I do it, you may think it is overkill. I have a temp controller, either built into the heather or you can pick one up from Home Depot for $25. I set a temperature of 78F with a variance of 1F in the heater controller NOT APEX. When my tank reaches 77F the controller clicks on and raises it back to 78F. You can keep it even tighter than this. Then I hook the temperature controller into my Apex with instructions of always on unless temperature of tank reaches 81F, then off. If heater controller fails in the on position, Apex will kill power. Besides this I also set alerts for myself, if tank reaches 76.5F and 80F. So I know if the heater has failed in the off position, or if the tank is starting to climb past my comfort area. This allows redundancy and two controllers managing the temperature of the tank.