In 3 of the 4 ponds by me, the fish may be toast.

Only one runs a diffuser to keep the water open. The other 3 have been sealed off with snow and ice for about 2 months now.

The 3/4 acre pond out my back door, may have a spot or two that maybe gets to about 7'-8' at best.

Don't know how thick the cover is on these, but I have meats stored in a steel cabinet in my garage that have been frozen solid for the past couple months.