Wintering Koi in Pond Zone 5ish Ottawa Canada

Hi All,

Got a pond of about 2000gal. Deepest spot is 4'10" about 3 feet around. I
will have ice covering the pond for approximately 3 months in the winter.
Do I have to have an opening in the ice for gases to escape? Should I heat
the bottom of the pond or the surface?

I don't intend to run the pump, filter, and waterfall for 3-4 months of the
year. I intend to submerge my plants at the deepest part of the pond over
the winter as well.

I just put the pond in this spring and spent many days getting the Ph and
buffering just right. The Ph is running between 7.8 while the buffering is
low at around 17. The only way to keep the Ph down was to drop the
buffering and keep very carful watch on the Ph. Ammonia, Nitrates, and
Nitrites don't register a reading. Salt is at 0.1%.

Use Kitty Litter as the base for the plants.

Fish Load:
5 Koi 4" long and 1 Koi 10" long. ~10 minnows, 2 perch, 3 blue gill, 2 bull
frogs, 1 painted turtle (1" diameter).

Plant Load:
12 cattails
2 Marsh Marigolds
4 very large oxygenators (got them from the lake)
6 Lily

I have a Tetra filter, highly over rated, and a Laguna 7000 pump.