Natural Pools and Koi Ponds


It’s not even Thanksgiving yet, but with steadily falling temperatures across the Chicagoland area, it’s time to start thinking about the rapidly approaching winter season. For those who have a natural pool or koi pond in their backyard, winter weather prep is even more important to get on top of in early November. By preparing now, you will ensure the health of your natural pool or koi pond throughout the winter, and decrease the amount of maintenance that’s needed after winter passes.

Natural pools and koi pond are beautiful and easy-to-maintain additions to any backyard, but they require very specific winter weather preparation protocols. At Reflections, we know how big an investment in a natural pool or koi pond can be, and our goal is to help homeowners understand how to protect and care for that investment. That’s why we’ve created this step-by-step guide to follow when winterizing your pool or pond.

Plant Care

How to Prepare Natural Pools and Koi Ponds for Winter

If your natural or koi pond has plants in it, how you prepare them for winter will have a huge impact on how “ready” your landscape feature is to take on colder temperatures. In fact, plant death and decay during the winter play one of the biggest roles in making a koi pond or natural pool dirty and cloudy.

First, remove any sludge and plant debris from the bottom and surface of the pool or pond. Consider placing pond netting over your body of water to prevent any organic debris from falling in during the winter. Then, figure out which type(s) of plant(s) your pond or pool contains: Water lilies or lotuses, hardy plants, marginally hardy plants, or tropical plants. Each type of plant correlates to its own unique winter care protocol:

  • Water lilies or lotuses: Both will survive as long as they are submerged deep enough that they will not freeze solid (usually a few feet). Just make sure to cut back the yellowing leaves first.
  • Hardy plants: As long as they stay submerged in the pond, they can survive even freezing temperatures. Usually, this type of plant does best closer to the surface of the pond or pool.
  • Marginally hardy plants: This type of plant can survive winter cold, but it will die if its crown freezes. To avoid this, you’ll want to submerge them below the ice/freeze line.
  • Tropical plants: These plants will not survive if left outside during the winter. We recommend that they be brought inside to function as houseplants until the cold temperatures pass.

Koi Care

How to Prepare Natural Pools and Koi Ponds for Winter

Koi are hardy fish. They can survive at very low, even freezing temperatures as long as the pond doesn’t freeze solid and maintains a high water quality. To keep them at optimal health, make sure you:

  • Begin to feed them a cold water fish food when the water temperature drops below 59 degrees. Reduce the amount of food you feed them as the temperature continues to drop. By the time the water is consistently below 48 degrees, you should stop feeding the koi, because their metabolism will be too slow to digest the food.
  • Add a cold water beneficial bacteria to the water to ensure adequate water quality. Also, consider adding pond salt.
  • If the top of the pond freezes over, it is important to maintain a hole in the solid surface. This will allow oxygen to flow into the pond, while noxious gasses can flow out. To maintain an adequate hole in the ice, we recommend using a pond heater/de-icer.  

Pump Care

If you have a pump in your natural pool or koi pond, it’s probably best to remove it, clean it thoroughly, and store it for winter. If you have a direct drive style pump, it should be stored in water and protected from freezing to keep the seals moist. If you have a magnetic drive or asynchronous pump, it can be stored anywhere dry.

Filters and Lights Care

Most natural pool and koi pond filters will survive the winter cold, but if you have a pressurized filter, you’ll want to remove and store it until spring. Make sure that filter pads and bio-media are cleaned and stored. UV lights should be unplugged, removed, cleaned thoroughly, and stored for the winter, too.

Waterfall Care

How to Prepare Natural Pools and Koi Ponds for Winter

For customers who live in climates that experience below-freezing temperatures (like Chicago), we always recommend they shut down their pool/pond’s waterfalls during late fall. Otherwise, ice dams are at the risk of forming, which can divert water out of the pool/pond and inadvertently drain their beautiful backyard structure.



Larry Carnes

Owner of Reflections Water Gardens

(815) 955-4911