Koi Fish Support

What do I feed my Koi?


Your Koi’s diet and nutritional needs will change with the water temperature. During the summer, you will need to feed your Koi a food that is high in protein, around 30% to 50%. During the spring and the fall, when the water is cold, you will need to feed your Koi a Wheat Germ based Koi food that is easy to digest. During the winter, Koi go dormant and won’t eat. If you keep your Koi in a tank inside your house during the winter, you can keep feeding them a high protein food.


How long do Koi live for?


Koi usually live for 20 to 30 years. Some will live even longer. Factors that affect how long a Koi will live include:

  • Overall health
  • Genetics
  • Pond water quality
  • Area Predator Population
  • Pond Size
  • Koi Food Quality
  • Environment


The oldest Koi on record was names Hanako. Hanako reportedly lived to be 226 years old.


When do Koi start breeding?


Koi will start breeding when they reach sexual maturity. This happens when they are at least two years old and about 12 inches long. If you plan on breeding your Koi, it is better to wait until they are around 4 or 5 years old. Spawning is stressful and it can damage your Koi. When they are older, they will be able to handle the stress better.


Why is my fish isolating itself?


Your Koi could have a parasite or a bacterial infection. It should be netted and inspected. If you live elsewhere and require assistance, get in touch with a veterinarian that specializes in Koi health in your area.

Do Koi do better in hard or soft water?


Koi do better in hard water.

A stable pH level is required to keep Koi. Hard water is full of minerals, which act as a buffer to prevent any pH fluctuations. It is easier to keep Koi in hard water than soft water. In a closed water system like a small Koi pond, the pH level will remain stable for longer periods of time with less water changes.

If you keep your Koi in soft water, you will need to do water changes more often, in order to keep your pH level stable. A “pH crash” can occur if you fail to do regular water changes. A pH crash happens when the mineral content in the pond water becomes too low to buffer and the pond water quickly becomes to acidic. A rapid change in the pH level is toxic to fish. Since soft water has a much lower mineral content than hard water, the chance of a pH crash happening is far greater.

We recommend that you use hard water for your Koi pond. It helps create a stable environment for the Koi fish.

More info at: solarserdar@gmail.


part of

Croatian Center of Renewable Energy Sources (CCRES)


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