My goldfish stay out in the fish pond all year long. We have terrible winters with temps below zero. I bought a small pond heater that kicks in to keep the ice from freezing over too much but for years I would just go out and chop a breathing hole for them when the temps dipped.
Year before last I put my inside goldfish out in the pond, I had kept him indoors for years. He does just fine.
Year before last I put my inside goldfish out in the pond, I had kept him indoors for years. He does just fine.