Ive just about had enough!!! Ive bought 3 Tetra Whisper Submersable heaters (the30-60 one 200 watts) for my 55 gallon and i cannont get the stupid thing to work correctly!!! Ive followed the directions to the tee and all it will do is bring my temperature up to about 74 then it shuts off no matter how high i crank it up. They say that in the middle position it will heat a 60 gallon tank to 78 degrees...If i turn it up all the way it will turn on for like 2-3 mins then shut right back off again without doing anything to the temerature...im at wits end!! Someone, please recomend me a better submersable heater or tell me what im doing wrong!!