Well I was totally late to winterize this year. We had a wedding by us last week which took up a lot of time with planning, and family around and everything, and the temps dropped really fast before I had a chance to winterize. I just disconnected my biofilter today because it hit a balmy 41 degrees today and it looks like it has been leaking out of a cleanout nozzle the last few days which is not a good sign, but I had been thinking of upgrading the filter for next year and I think I'll need to do that for sure now. I put in my pond breather today, still have my mini koi airstone going and one pump running to keep water moving.