Koi in winter

Tips to keep your fish healthy

Whether you stay in warmer climates or in colder regions, winter will most probably see a difference in day temperatures. In South Africa we have a wide variation of winter temperatures to deal with, but the good news is that koi fish will endure all our weather conditions. If you care about your koi, follow these tips to keep them and your pond in good condition in winter.

Koi in winter

June 25, 2019

Pond management

The colder temperatures in winter do affect the koi’s behaviour in that they slow down or go into a hibernation phase. Most of the time, when temperatures are lower than 8°C, they will either swim slowly or lie at the bottom of the pond. It is for this reason that you need to do the following:

  1. Keep the pond clear of all falling leaves and keep debris from collecting on the bottom of the pond, as this rotten material may cause harmful bacteria to attach themselves to the resting koi.
  2. Make sure that your pump basket is cleaned regularly, as the falling leaves may cause blockage.
  3. When temperatures drop below 8°C, switch off venturi and any waterfalls into the pond, as this will make the water even colder.
  4. Remove any air stones.

Koi feeding

  1. Gradually slow down your feeding as the temperature decreases and stop feeding altogether when the water falls below 4°C.
  2. A koi doesn’t have a stomach, he has a long intestine. So, during hibernation at these cold temperatures the food cannot be digested and can cause internal bacterial problems.
  3. When feeding and depending on the temperature of the water, the food should be eaten within 30 minutes. It is normal to reduce feeding to once a day or even once in two days.

 Koi health

  1. When the water temperature drops below 2°C, it is then critical for the koi, as ice can form within the gill membrane (their lungs). In such cases I would suggest adding 10% new water to increase the water temperature slightly.
  2. Sometimes ponds are totally frozen on the top in winter with the koi resting at the bottom where the warmer water is. They are quite comfortable, so don’t panic.

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