You will need to keep an eye on the water temperature with a pond thermometer. Once the water temperature is below 50 - 55'F , you need to stop feeding them completely. Goldfish are cold blooded, which just mean they get their heat from the environment in order to help digest food. Once the temperature drops below 50 - 55 ' F ,their digestive system slows down a lot. So don't feed them once the water is around this range or the food will just stay in their guts and rot, which will kill them.




When your pond's water is consistently around 55-60 degrees F, you can feed them a low-protein food only (most of your spring/fall or winter feeds have low protein contents). Once the water temp drops below 50-55 F, stop feeding them entirely. You can feed them for a  couple of weeks on a medicated food , like Medikoi,  prior to stopping the food for the winter just to give their immune systems a boost before they go into hibernation.


As for when to feed in the spring: nothing until the water warms up to at least 50-55 F on a consistent basis, and then a low-protein-only food until the water gets up to around 60 degrees to get their digestive systems used to processing food again. Then, you can switch to a good high-protein pellet food like Hikari or Aquatic Gold, and add treats that koi and goldfish really enjoy such as fresh fruits and vegetables, and things like krill and bloodworms.


The only other thing you need to do to overwinter your fish is make sure your pond doesn't freeze completely over. Goldfish can survive in very cold water , but they can't survive if the pond turns into a block of ice.

My apt has a sunken tub outside with goldfish or koi.  there is a small fountain, but the water will definitely freeze here in NYC.  I suppose the fish must be moved inside?  st*pid questions, perhpas, but how much room do the fish need and does the water have to be pre-treated?  One of the fish is about 5 inches long. thanks.