i have 2 of the same type heaters they are both 250 watt and i wanted to use them both on my 75 gallon tank one in the sump the other in the over flow, i want to do this just in case one malfunctions. i was just curious wouldn't putting 2 heaters just heat the tank faster and possibly over heat it or if i set them both to the same temperature they will just heat until one point and both shut off? sorry prob a stupid question