When water temperatures remain below 60 degrees for more than a few days, goldfish enter into a period of dormancy. They slow down, stop eating and hover at the bottom of the pond. Goldfish can survive several months of hibernation, but you should feed them slightly more than usual in the months leading up to the winter. When the temperature cools, begin feeding less. The temperature must drop gradually for fish to adapt. Never move indoor goldfish outside during the winter or place goldfish outside after you've moved to a cooler climate.