Guidelines for Koi Pond Fish in Winter

Koi Fish Winter Koi Pond Care

The steps you take to properly shut down your koi pond in the winter will determine the quality of your koi pond water and the health of your koi fish and pond fish in the spring. Plus, it could be the difference between losing koi in the cold winter months or not.

Shutting your koi pond down in the winter

“What is the best date in the fall that I should shut down my koi pond for the winter?”

The answer is:
Shutting your koi pond down in the fall is not set to an exact date; it all depends on the temperature of your koi pond water. Some fall seasons are much warmer than others and your pond water will stay warmer longer, some fall seasons are colder and your pond water will cool down earlier.

A good rule of thumb is to shut your koi pond down when you stop feeding your koi.

When should I stop feeding my koi fish in the fall?
Stop any feeding of your koi for the entire fall/winter season when your koi pond water drops below 55° F and stays there for ten to fourteen days, day and night.
Once you stopped feeding for the fall/winter season.Do Not feed your koi even if your pond water temperature rises.

There are two major reasons why you stop feeding your koi when pond water temperatures drop below 55° F.

1- The metabolism of your koi starts to slow way down with pond water temperatures below 55° and your koi can not digest their food. Your koi do not have a stomach, just a long intestinal tract; the food lays in their digestive tract and rots, causing death.

2- Even if your koi could digest their food at colder pond water temperatures of 55° or below, their waste would produce deadly ammonia in your koi pond water “that’s the last thing you want going into a winter shut down”. Plus, feeding your koi below 55°F will cause your ammonia levels to rise because the “Good Bacteria" that removes the “ammonia” from your pond water keeps slowing down under these cold water conditions and eventually stops functioning. DO NOT feed any kind of food with pond water temperatures under 55°F

How do I treat my koi fish and pond fish for proper winter pond care?

1- Thirty to sixty days before your pond water drops below 60° F, watch your fish for signs of “flashing” (rubbing off rocks and the sides of the koi pond). If they are “flashing” treat them for flukes with Aqua Meds® Aqua Prazi™. If they continue to “flash”, treat them with TERMINATE®. Feed Med-Koi for 10 to 14 days for any bacterial infections.

NOTE: Many Pond Keepers that do not have a microscope to verify parasites, practice the above treatment as a guarantee that their fish will be free of parasites and any bacterial infections before they go down for their long winters nap.

How do I prepare my koi fish pond for proper winter pond care?

1. Thirty to sixty days before your pond water drops below 60° F vacuum the bottom of your koi pond to remove all leaves, sludge and waste. Do a 25 to 50% water change using a good de-chlor like Aqua Meds® De-Chlor and More™.

2. When you stop feeding, shut off and drain all your water pipes, filters, U.V.s and pumps to prevent freezing and cracking. Leaving the cold water in your koi pond circulating around your koi will reduce their body temperature.

Many koi in the middle Atlantic States (MD,NC) were lost one winter because of the unusual harsh winter storm that hit the middle east coast. The deaths were caused by the fact that many pond keepers had their filters running, circulating the extra cold water around their koi at the bottom of their pond and they chilled their koi down so low it killed them.

3. If your koi winter pond freezes over, prepare a method for keeping a small hole in the ice. This can be done with a heater or an air source. The preferred method used by most pond keepers is using a large air stone or aerator. The reason is, it’s less expensive to run all winter than a heater and is better for your koi pond fish because it helps remove any toxic gases that might form in your koi winter pond under the ice.

Place the aerator within six inches from the surface of your pond water. The aerator will keep an opening in the ice if it develops. The reason to raise your aerator to the top is to keep it from circulating the cold water around your koi at the bottom of your koi pond.

What Aqua Meds® products should I use over the winter and why?

Two time tested Aqua Meds® products that can really improve the survival and health of your koi, plus, the quality of your winter pond water are, Arctic Blend™ and Aqua MedZyme™. Aqua Meds® Arctic Blend™ and Aqua MedZyme™ are considered the best winter pond care treatments on the market, because they work.

Arctic Blend™ is a new generation of cold water bacteria. Arctic Blend™ is a 100% natural bacteria that contains microbes that remove deadly ammonia and other toxins from your pond water.

Plus, Arctic Blend™ has a sludge remover to help keep your pond clean all winter. Start using Arctic Blend™ when the temperature of your pond drops below 60° F.

Q- My koi are not producing any waste because they are not eating in the winter. No waste, no ammonia. Why should I be concerned about ammonia in my koi pond water in the winter?

A- Your koi produce more ammonia from breathing than from their waste. They are breathing all winter long producing ammonia, however, your “Good Bacteria is “sleeping” because of the cold water and will not remove the deadly ammonia from your pond water.

Q- How can Arctic Blend™ remove the ammonia in my koi pond water at very cold water temperatures and the “Good Bacteria” in my filter can not.

A- Arctic Blend™ is not the same bacteria that are found in your filters. The Arctic Blend™ microbes are found in the cold waters of the Arctic Ocean and can perform at temperatures as cold as 35°F. Please visit our web site: for more details.

Aqua MedZyme™ renders deadly ulcer causing Aeromonas, Pseudomonas harmless to your koi. Aeromonas, Pseudomonas thrives in your koi pond at pond water temperatures of over 40°F. The immune system of your koi is very weak at low pond water temperatures and the Aeromonas, Pseudomonas take advantage of your koi at this time.

Aqua MedZyme™ helps your koi fight off their deadly attack. Treat with Aqua MedZyme™ when water temperatures are above 40°F. Please visit our web site: for more details.
Just by following these few simple winter koi pond care guidelines your koi will come through their long winters nap in great condition.

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