Summer is gone and spring is a ways off. However, the business of keeping koi never ends. A little maintenance before winter sets in can make it an easier transition to spring once temperatures start to rise. Fall maintenance also helps for a cleaner environment for your koi as they slow down in preparation for winter.

Here are some of the items that should be addressed as the water temperatures in your koi pond start to dip below 60ºF.

Pond Cleaning

As leaves start to fall, having a net across the surface of the pond is extremely helpful in catching foliage before it gets into your pond. Some koi keepers use pond nets that have the additional benefit of “dissuading” predators. Once the fall is over, they can be rolled up and put away for the winter, especially if the pond freezes over.

Pond Skimmer

Don’t forget to clean out your pond skimmer! It will have a good crop of fallen foliage in it throughout the season.

A leaf net is another handy tool to remove floating foliage. It can be used on shallow ponds to clear the bottom too.

Pond Vacuum

There is a range of pond vacuum options available. Although it might not be used often, a quality pond vacuum is a great way to clean off debris or waste that filters or drains might have missed.

Pond Plants

koi pond with pond plants
At the park by RubyGoes by cc 2.0

If you have plants in or around your pond, they will need a little maintenance to help keep them healthy and to free your pond of any detritus that can affect water quality in the colder months. Any plant life left in the pond can impact water parameters and release toxic gases.

Plants around pond

If you have leafy plants around your pond, trimming them back as the weather changes can help to keep falling debris out of your pond.

Aquatic Pond Plants


Tropical and subtropical plants should be brought inside. Hardy plants can be trimmed and moved deeper into the pond.

This article from offers additional information on how to care for your plants according to their respective “hardiness” (as determined by the pond’s temperature range).


As water temperatures begin to drop, so does your koi’s metabolism. With that metabolism shift, they won’t require as much food.

It also means that anything they eat will remain in the digestive tract for longer. The longer food is in the stomach, the higher the risk of intestinal infection. Consider switching to a more readily digestible food type that still offers the required nutrition, like a higher wheat feed.

Some things to remember about fall feeding:

  • Under 70ºF a koi’s digestive system starts to slow down
  • When in doubt feed a little less
  • In cooler months, feed koi during the hottest part of the day

Feeding And Temperatures

Late-season feeding schedules tend to be somewhat subjective for koi keepers. Koi kichi know their koi and ponds better than anyone and will decide when to feed (or not to feed) based on experience. These ranges, frequencies, and food types are based on accepted norms.

Water Temperature Frequency Type
55-68ºF 1-2/day Wheat germ
41-55ºF 1-2/wk Wheat germ
>41ºF Stop feeding n/a

Food Storage

At the end of the season, you may have some cold-weather koi food left. Do you keep it or pitch it?

Always keep food in a cool, dry place out of direct sunlight. Storing it in a well-sealed container helps to preserve it for longer, even after regular feedings have stopped.

Many koi keepers opt for airtight containers and will portion the larger bag of food into smaller resealable bags, which they then store in sealed containers.

Refrigerating your leftover food can cause ice crystals to form in the pellets. Once this food is brought back to room temperature condensation will form, causing mildew and mold—especially if the thawed food is in larger quantities. It can also contribute to protein-heavy food turning rancid.

After six months, some of the vitamins in the food will erode. Some enthusiasts use the sniff test to make sure that the food is still good. But if the food is older than six months, it is probably a good idea to buy a new bag.


Fall is a good opportunity to get your filters in order.

If you expect cold winters, getting your mechanical and biological filters prepped can help you jumpstart them in the spring.

When cleaning the media in the filters, remember that it doesn’t mean they should be completely cleaned. Although beneficial bacteria will start to slow their functions when temperatures drop below 60ºF, they will continue to work in a much-diminished capacity until the water temperature starts to rise above 60ºF.

Remove much of the heavy waste in the filter with a gentle clean, but brown media doesn’t mean bad media. As beneficial bacteria grow, they will discolor the media.

Cold Water Beneficial Bacteria

Cold water bacteria is another one of the topics that split opinions amongst koi kichi. Adding liquid beneficial bacteria reportedly boosts a koi pond’s ability to deal with waste more effectively in cooler fall water temperatures.

However, many believe that these cold water bacteria might be an unnecessary additive to aid in cleaning a koi pond in the fall. Others believe that adding cold water beneficial bacteria is a viable and useful precautionary measure to help with water quality.

Even a small amount of pre-winter cleaning and maintenance can go a long way to a much simpler transition for both you and your Living Jewels.

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