I've been using a Pro Heat II for a year and a half with great results. The heater keeps the water at a consistent 79.5 degrees (I check with two other thermometers). The only problem with the unit is the thermostat's sensitivity. It is very easy for me to knock the dial one way or another while I'm fidgeting underneath the tank. I quickly learned a piece of electrical tape does a good job of keeping the dial in place.