Shutting down or preparing your fish pond for the winter is typically referred to as 'winterizing' your pond. This involves a process which prepares your fish for freezing temperatures and a lack of access to food. Some fish are better at surviving winters than others, do some research to make sure that yours can withstand the winter temperatures in your climate. Most fish require a few feet of open water underneath the surface layer of ice, so make sure your pond is deep enough to provide that room. Fish enter a period of dormancy in the winter where their metabolism slows significantly as there is less access to food. Take temperature readings of your pond, and reduce the frequency of feedings once it drops to about 50 degrees.
Cut back excess vegetation and trim any marginals so that they're a few inches below the water's surface. Make sure to remove any debris and vacuum out muck and sludge from the bottom of your pond. This will reduce the amount of organic material decomposing through the winter, which can produce harmful gases.
