I bought a new eheim jager heater - put it in my tank and let it sit for at least a half hour before plugging it in. Before doing so I set the thermostat (blue dial) to 77 degrees. Plugged it in - and it raised the temp to 77, 78, 79, 80 - and kept going... The red dial will only adjust to 4 degrees above the desired temp that the blue ring is set at - so that is totally worthless !! I bought it off amazon and tried to contact Ken's Fish in Massachusetts that it was bought from and got voice mail - called twice and left messages both times - sent email - and no response to either voicemail or emails. Then I see eheim has a facebook page - so I post about the problem on that - and moments ago get a response from them asking if I followed the "manual" exactly by letting the heater sit in the tank for 24 hours before attempting to use it. It does not say anything about it being in the tank for 24 hours before using it.....so what's with that???? All it say's is to monitor the temperature in the aquarium for 24 hours with a thermometer . So what part of this equation am I missing or do I not understand? I would think that if the blue dial (desired temp) is set to 77 degrees it should heat to within 1 or 2 degrees of that - not 10 degrees. I really think this thing has a bad thermostat or it wouldn't be doing this. What do you folks think ??