fishin4cars
True friends just call me Larkin
36" will work fine for ponds that don't freeze solid, or just barely freeze solid and have a good air supply to keep a hole in the ice. Solid freezes and ponds that will be iced for more than a week need to be deeper than 36" 48" would be minimal I would consider, 5'-6' is really more realistic and a must if your even thinking about keeping koi out doors over the winter!