Koi Keeping in Autumn – How to Best Prepare Your Koi for Winter

Even as temperatures drop, you should not abruptly stop feeding your Koi in autumn; instead, adjust their feeding according to water temperature.
As long as the water remains above 10 °C, you can continue feeding a light, easily digestible autumn diet. If the temperature approaches 8 °C, gradually reduce the feed amount and stop feeding entirely when the Koi no longer accept food or when temperature falls below 8 °C.
This targeted conditioning is important to build energy and nutrient reserves for Winter. Doing so helps prevent issues such as springtime energy deficiency syndrome — a common issue when Koi emerge too weak from Winter.

Tip: It is better to feed several small portions throughout the day rather than one large meal. This aids digestion and ensures a steady supply of energy. Click here for a blog post on feeding.

Autumn is the last opportunity to detect and treat health issues in your Koi.

Watch your fish closely: does one exhibit unusual behavior, skin changes, or rubbing motions? This is the right moment to identify the cause — ideally together with a veterinarian specializing in Koi — and treat it.

You should not introduce new Koi at this time, because temperatures are too low. Transport and acclimatization would overly stress their immune systems, and in case of problems, it would be difficult to intervene.

Leaf cover nets are indispensable in autumn to keep leaves, branches, and debris out of the pond. Large leaves from maple, oak, or walnut, for example, can easily get stuck in pumps, bottom drains, or skimmers and disrupt water flow.

If leaves fall into the water and decompose, they release decay gases and nutrients that promote algae growth and reduce water quality. With a leaf cover net, your pond stays clean, the filtration system is relieved, and you save significant cleanup effort in spring.

Koi should not overwinter below 5 °C. Large temperature fluctuations or overly low temperatures cause stress to the fish and strain their metabolism. A constant water temperature is therefore essential — and easily achieved with the right technology.

Here are some proven solutions (available at koikichi.ch) to support you:

• Elecro Cygnet Koi Pond Heater analogue 2kw
  Ideal for small ponds. Precise temperature control, robust stainless steel design, and easy installation. Perfect for ponds up to approx. 10'000 liters. Premium device with flow switch.

• Aqua Forte professional pond heater stainless steel (1,2 & 3 kW)
  Robust flow heater for larger ponds. Thanks to the various power settings, you can adjust it to suit your pond size perfectly. Budget-friendly device that is easy on your wallet.

• AquaForte pond & pool heat pump Mr. Silence
  The premium solution for energy-efficient pond heating. Very quiet in operation and particularly economical—ideal for year-round temperature control and compensation for temperature fluctuations. Also perfect for extending the season.

• Pond Heating tape 20m
  Can be laid evenly in the pond or in the filter. Ideal if no structural adjustments to the piping system are desired.

• Schego pond heater 300W
  Ideal for smaller ponds or for keeping an ice surface open. Compact, efficient, and reliable.

Whether your pond is small or large, a pond heater protects your Koi from thermal shocks, stress, and winter diseases. They thus safely pass through the cold season and start spring full of vitality.
If you’re unsure which system is best for your pond, we’ll be happy to advise you personally.

koikichi.ch – your partner for koi and pond technology in Switzerland

Tip: Cover your pond to save energy. For instance, PE balls that insulate the water surface, or a simple greenhouse-style cover built over the pond using poles and plastic sheeting, can be effective.

Autumn is the most important time to optimally prepare your Koi for Winter. With correct feeding, a well-maintained filtration system, stable temperatures, and healthy fish, you set the stage for a relaxed Winter and a good start in spring.

Those who work carefully now will face less stress later — and enjoy strong, vital Koi for a long time.