I have a 10-30 gallon heater in my 10 gallon tank and I'm wondering about how much it should be running. It's set to run every time the internal thermometer detects the water is below 78 degrees. However, it's constantly on. It'll turn off for a few minutes here and there but it's mostly on. Is this okay? I know it's meant to heat the water but do you think it'll take a toll on my electricity bill? Haha.