So first of all I have to agree with another review that the picture is wrong. It is only on the device and + - printed characters, but not the numbers ° C. In my case it is a little worse, the heater does not heat up and you can see it from time to time short sparks in the glass. How dangerous is that now I do not know, but I maintain that it can not be dangerous. (I do not mean that the warning light but real spark !!!). The part I return and it all depends but again a little expensive EHEIM / hunters into the pool ... I can not recommend the heating rod
