Hi guys, I just recently purchased a 125W of the whisk Hager heater for my 40 gallon tank running with a 10 gallon sump. I thought a 125W heater should be enought because it is for 40~53gallon. And I set the temperature at 82°F for the first day and let it run for 24 hours, but my thermometer showed only 77°F , so I calibrated it by Turing the red arrow to 77°F and turn the blue part to the 82°F again. After another 24 hours, the thermometer still showed 77°F. I wonder what's the problem? Btw, I placed my heater in the buttom of my sump not in the display tank.