Hi, I have a 10 gallon tank with a 100watt heater it supposed to be about 78 degrees but reads 77.2 degrees and the red light keeps going on and off meaning it's supposed to be heating up. The room temperature is about 65 degrees. I live in upsate ny and it's cold here right now. I also have a 5 gallon tank with a 100 watt heater reading 77.5 degrees when it's preset at 78 degrees and the light also going on and off. One tank has betta the other a 2 African dwarf frogs. I guess I'm just wondering if I need to switch my heaters to a higher wattage due to it being colder here?