Now I have had a 500gal pond for several years now. My Koi and turtles have made it through winters fine. I was debating dropping my red-tailed catfish in the pond. He is roughly a foot long. I understand he needs around 85 deg water which is not a problem during summer months. I have been exploring solar/ glass/ heating elements to keep the water warm over the winters, all to no avail. Has any one ever tried this before or wasted cause???