To use an aquarium heater effectivly you need to have the water propeerly circulate the tank. The water around the heater may be at the right temp but the rest of the tank could be at a cooler temp. I placed my heater near the middle of my 55 gallon tank. Then I have the outlet nozel from my fluval g4 canister filter helping circulate water. Also my 2 HOB
aqueon filters and 1 marineland 400 power head help circulate the water. My water is usually around 77/78 degrees fahrenheit when I check thee temp on my Fluval G3 filter.