I got this heater about a month ago but just put it in a tank tonight. I filled the tank and then put the thermometer in, it read about 76. When I put the heater in, it wouldnt come on until the dial was to at least 79. Then I tried some different temperatures. Sometimes it would come on at 80, 81, etc then if I moved the dial and the moved it back to the temp I just tried, the light stays off. Im thinking this is a screwy heater. Right now its set at 79 so I'll wait till tomorrow and see what the temperature is. If the temperature stays constant, what would you do, keep it or try to exchange it? I want to keep it if possible because I need to move a fish from one of my other tanks.