10/16/2026
Do you need to winterize your outdoor koi or goldfish pond? It may be easier than you think! Outdoor goldfish can survive the winter as long as your pond is deep enough, water quality is maintained, and you prepare in autumn.
Goldfish and koi are both hardy types of fish and will go into "torpor" during the cold season. They rest at the bottom of the pond, and their digestive systems slow down significantly. To prepare them, reduce feeding as pond temperatures drop into the 40s (Fahrenheit) and stop feeding altogether once temperatures drop below this. In spring, begin small feedings at this temperature and slowly increase until temps warm back up.
If your pond is at least 3 feet deep, it will naturally provide an oxygenated refuge, more consistent temperatures, and should not freeze solid. Make sure to leave any filters and aerators running through winter to help prevent your pond from freezing solid. Also ensure there is enough water per fish; usually, ~250 gallons per koi or large goldfish is enough.
Avoid agitating or disturbing the water during the winter (e.g., do not break up the surface ice). Shockwaves and abrupt temperature changes can harm and, in some instances, kill the fish. Lastly, check your pond periodically for ice damage, predators, or water quality issues.
