We are a little late in figuring this out, but I've read too much online and now I'm more unsure of what to do than before. We just got our pond completely finished in early September and then winter came early. The pond is approximately 500 gallons, and two feet deep with a ledge that's about 1 foot under the surface. We have a submerged pump encased in filter material hooked to a bubbler rock which produces a lot of water movement. We've had ice forming on the surface and the bubbler is still going strong so far, but we don't want anything to freeze and break. (The bubbler rock sits on another ledge.) We are pretty sure we need to unhook and remove the pump, but we aren't sure if we need an aerator, or if just a deicer will be sufficient for the winter.