Brian,

Tell us how you did it and what kind of system you used. Aerating incorrectly in winter can almost be as bad as not aerating at all.

I had some losses and stressed fish my first severe winter when I aerated incorrectly. My mistake was to aerate in the center of the pond in the deepest water with a system that is almost too big for the pond. You can't mix too much in the summer but you can mix the water column too much in the winter. I use a 1/3 hp compressor that puts out 4.2 cfms in summer but back down to a .8 cfm compressor in winter. That one winter I had problems I was using the 4.2 cfm compressor with two diffusers in the deepest water. That was too much mixing for winter.

In winter your water gradually warms up the deeper you go to about 39 F. or a little more. Warmwater fish need this relatively warmer water in winter. and if you mix the water too well there is no warm water santuary and they become stressed.

Do you have a lot of aquatic weeds in the pond? Did you get deep snow on top of the thick ice? You may have had a die off of aquatic weeds resulting in decomposition that used too much oxygen.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.