Join Date: Jun 2011
Location: Lake City, Florida
I have a 300W in a 120 gallon, same thing, one night it jumped to 88 degrees (luckily it's a Discuss Tank). I unplugged it and got the tank back down to 82 by slowly pouring cool water over the circulation pump. Couple days later I lowered the setting, plugged the Hydor back in and slowly brought back up, knock on wood it has not happened again.