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This information is provided by Provet for educational purposes only.

You should seek the advice of your veterinarian if your pet is ill as only he or she can correctly advise on the diagnosis and recommend the treatment that is most appropriate for your pet.

As environmental temperatures fall the activity of outdoor fish decreases and feeding can be stopped

Fish do not hibernate like mammals, but as environmental temperatures fall their metabolic rate and activity decreases, they go into a stupor and stop feeding. They usually adopt a position towards the bottom of the pond. It is important that there is enough depth to the pond so that all the water does not freeze. Usually 3-4 feet is adequate. Providing your pond filtration system is effective,  your pond has been well stocked with plants and is well aerated you should not have any problems.

If the winter is particularly mild and the fish remain active feeding may be required throughout the period. The rule is feed the FISH not the POND. When in doubt do not overfeed as that simply adds waste to the pond. 

Having said this owners and breeders do have different opinions about how to over-winter fish. Some examples of recommendations that Provet has come across include :

  • Bring the fish indoors in the winter. House them in a deep barrel of water. This may be appropriate for valuable Koi carp
  • Add a heater to the pond - surface heaters can apparently be bought quite cheaply
  • Dead plants should be removed from the pond as they will rot adding waste toxins to the water
  • If the pond surface freezes over entirely cut a hole in the ice to allow waste gases to escape
  • Add a chunk of polystyrene to float on top of the pond. This will prevent the surface from icing over completely and allow gases to escape. It can be weighted down by attaching it to a brick.
  • Logs of wood added to the surface of the pond may achieve the same purpose, and may provide an area of relative warmth near the surface of the pond.
  • Fill a plastic bottle eg a milk bottle with hot water and place it on top of ice to melt it. Do not smash or otherwise break the ice as this can kill the fish (sent in by a visitor to Provets web site)
  • Cover the pond with a sheet of bubble wrap (sent in by a visitor to Provets web site)
  • Float a tennis ball on the surface of the water to stop the top freezing over completely (sent in by a visitor to Provet)
  • I`ve found  one of the best ways to keep a pond  ice free , as well as the usual heaters etc, is to place a sheet of  BUBBLE WRAP over  the netting  but under the FILTER  PIPES  etc.Why don`t you try this and this way you can still feed the fish
    because the water is kept a little warmer. (sent in by a Koi breeder visitor to Provet)

Provet Feedback Request

If you have any other recommendations for over-wintering fish in ponds please send them in to 

Thank YOU


Updated October 2013