I will be buulding a small pond soon, about 550 gallons. I plan on keeping a couple of turtles and a few large fish in it. How hard would it be to keep the water at a decent temperature during the winter? Can u use a few large aquarium heaters and a de-icer? I live in southern Kentucky and the winters here vary a bit, some days can be in the 20s or 30s, and some days down in the single digits. Would 4 or 5 of the 450 watt version of this work? http://www.petmountain.com/product/...p-digital-heater-with-temperature-sensor.html