He's so cute! I have a 750 gal pond with koi and
goldfish (once feeders and local kids' science projects). It freezes over the top 3 inches in the winter, but not completely. My koi have not been an issue, but the larger goldfish are carnivorous. The smallest has about a 6" long body. They eat large moths, snails, and up to 1" (body) goldfish. If you have lots of plants and spaces in rocks, I'd give it a shot though. I believe in "survival of the fittest". Some won't agree with me, but it's better than a jar, a carnival (miserable death), or stunting unhappy aquarium. Feed the others before putting him in. Put him within a plant or crevas.
Good luck.
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