I have an AC Jr. I use it to control my lights, cooling fans and heater. I am happy with it. It maintains my temperature +/- 1 degree F. It will turn off my MH if the fans fail. It has more features than I need but gives me peace of mind that I won't cook my tank. If I could find an inexpensive used ACIII i'd buy it since it would talk to my iPhone (but that because I'm kind of geeky at times
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