I've had my setup for almost a year now but for the last 4 months I've had to start over. Been cycling, now have plants and a sucker fish, water is always 78. Yesterday afternoon I did a 25% water change as usual but also cleaned the filter which took a little longer than usual. Plugged everything back. Late last night I noticed my water was at 92!! I unplugged the heater but left it in the tank. It's a regular one dial heater with Low and High. Now that it's at 79 today on its own, I put the heater dial to the lowest notch and plugged it in (planning on upping it until the light turns on and then back one) but the light comes on right away, on the lowest temp??? Any thoughts?