Hi all! I have a visi-therm 200 marine land heater I bought yesterday in my 55 gallon tank. What I have noticed is that the temperature dial on the heater varies significantly from the digital thermometer in my tank. Digital thermometer reads 79 whereas the heater is only set to 72 on the dial. Should I be worried about this big of a discrepancy? I have an infrared thermometer which when I point and shoot reads 79 along the water and side of the tank. I am thinking the water is closer to 79. I am running two Aquaclear 70s and a sponge filter in this tank. Could the level of filtration be heating up the water?