905-715-2447 Winter Hours: Call for Appointment 2474 Line 9, Bradford, ON Canada

7 Steps to Koi Winter Survival

7 Steps to Koi Winter Survival

Winters in most of Canada and the northern United States are usually quite long and cold, even without a Polar Vortex!. Koi and goldfish are at their most vulnerable during the winter because their metabolisms are slow and their immune systems are very weak. On top of that, the pond water quality has the greatest chance of becoming unlivable because of low oxygen levels, elevated carbon dioxide, ammonia and nitrite levels.  If proper steps aren’t taken in autumn, there is a good chance that your fish won’t survive the winter. Luckily, with some extra planning, care and maintenance you can help ensure your fish thrive through the long winter months.

  • Feed a Cold Water Fish Food – Once the water temperature in the pond falls to 64 F / 18 C, begin feeding a Spring & Fall koi food. The main ingredients found in these foods is wheat germ, which the fish can digest easily, especially in cold weather. Stop feeding the fish when the water temperature falls below 48 F / 9 C.
  • Keep Tree Leaves Out of The Pond – Tree and garden plant leaves that fall in the pond will add tannins to the water making it dark and murky. They will also produce ammonia and nitrite and consume oxygen as they begin to break down and rot. If left in the pond during the winter the water will become toxic to the fish. It is much easier to put Pond Netting over the pond to keep the leaves out, than having to net them out once they have sunk to the bottom.
  • Remove Sludge From The Pond – fish waste, dead algae and plant matter can settle on the bottom of the pond and form a layer of sludge. This organic matter can continue to break down during the winter causing the same water quality issues mention above. Use a fine mesh Pond Net or Pond Vacuum to remove as much sludge as possible.
  • Partial Water Changes – Performing partial water changes (up to 25%) will help to improve water quality by flushing out and lowering nitrates or other unwanted compounds or toxins that may have accumulated over the summer as well as replenishing essential minerals. always remember to use a Dechlorinator is you are on town water.
  • Add Cold Water Beneficial Bacteria – Cold Water Beneficial Bacteria and enzymes are designed to break down any remaining leaves, residual sludge and organic matter in the pond even in winter. They sustain biological activity in the cold water and to help maintain good water quality.
  • Add Salt – Salt  provides many benefits to the fish including making osmoregulation easier, reducing nitrite toxicity  and killing many common parasite (at higher concentrations). Add 1 to 2 lbs of Pond Salt + Buffer or untreated salt per 100 gallons of pond water.
  • Maintain a Hole in the Ice –  Keeping an opening in the ice allows oxygen into the pond and noxious gasses such as carbon dioxide out of the pond. If a pond freezes over completely the surface is essentially sealed. The fish will have a limited supply of oxygen that has to last for the entire winter until the ice melts again in the spring. The more fish you have in the pond, the faster the oxygen will run out. Large fish (and usually your favourite fish) are usually the first to die as a result of ow oxygen.  We recommend a floating Pond Heater / De-icer combined with an Pond Aerator to maintain a hole(s) through the ice.

For more in-depth information see our How to Winterize Your Pond and How to Build a Winter Pond Cover information pages. Or if you are concerned about leaving you fish in the pond during the winter, you can always bring them inside where you can keep a close eye on them. See our Bringing Koi Indoors For Winter for more information

We have all the Fall and Winter Pond Supplies  you need to prepare your pond for winter and help ensure your fish survive.

About the author

Graduated from the University of Guelph with a B.Sc. (Hons) Marine Biology. A passion for fish, ponds, marine aquariums and water features to compliment his 30 years experience of fish husbandry. Previous work includes Ripley’s Aquarium, the Toronto Zoo, Bass Pro Shops, Rainforest Cafe and the National Museum of Kenya.

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