I'll post another pic without the snow & you can see how i do gas exchange during the winter with just a small air-pump instead of those EXPENSIVE TO RUN heaters. I'm retired & very cheap.....Rich
I got a new heater, cost 55 bucks, only uses 100 watts. very satisfactory so far.
Pond frozen over for 3 weeks, it melted through, and i sould see at least some of my fish have survived.
I have 4 koi in my puddle that are just shy of 2ft. & have survived & flourished with my arrangement. I tried to add another pic, but it would'nt load for some reason. Oh well.......Rich