I have four big goldfish and a bunch of young. I went out to my pond on 12-10 just to take a look and saw a large number of my fish feeding. I was surprised since we had just had about four days of temps in the mid teens for lows and highs in the mid 30's to low 40's. A most hardy fish I see. There was even a thin ring of ice all the way around the pond that was about 9 inches wide.