I'm finally building a new pond/pool for my ducks. It is going to be 5' x 6' x 18" deep or about 337 gallons of water. I want it to be swimmable all winter long so I've been researching heaters and aerators. My understanding is even though a heater may be submersible as this one is it will only keep a hole in the ice sheet for fish to breath not keep the entire pond/pool unfrozen. http://www.123ponds.com/kh8100.html I remember awhile back I asked about heating/aerating and someone suggested getting an aerator to keep the water moving and unfrozen instead of using a heater. I live in Central MA zone 6 where the average winter temps are 0 - 30. Will an aerator really work in freezing temps to keep the entire 337 gallons unfrozen?