I use an Aquacontroller III. A good investment for a large tank and imo worth every penny. It has saved me many times from the tank overheating due to lights, etc. Everything runs much more stable. In what I would have spent on single timers, temperature probes, as well as pH controllers/monitors - the cost is not that unreasonable. And the great thing about it is I can monitor the system from remote if I am away on vacation.