I was wondering if a heater is necessary for goldfish? They don't have one currently and have been fine at room temperature for the past 3 months, but I have an extra Visi-Therm Deluxe Submersible Heater 200 watt heater laying around. The thing is it's for tanks up to 55 gallon. Would this heater be way to powerful? If so, I might considering picking the same heater in the 75watt variant. It's only $18 locally. EDIT, I googled around and it appears it's not necessary since they are cold water fish.