This is an observation I had, no science behind it. I had a tank with 20 green sun fish in it for cat fish bait. Over winter it froze solid, you could see the sun fish laying flat on bottom. Thought they all died, but in spring over half were still alive. If you have a pond that tends to winter freeze. I would put in a cross of some sort with the Green sunfish. The fish were not fed and were in a large stock tank with some green algae growing in it.
