Koi food. Feeding koi throughout the year

Q: I am aware that there are many different types of Koi food available, which seem to offer different benefits to my Koi. What is the purpose of the different foods? Should I change my Koi’s diet at different times of the year? Should I stop feeding my Koi altogether in the winter? What are the best ways of ensuring that my Koi get a balanced diet throughout the year?

A: Koi rely on us entirely for their health and well-being. We must provide our koi with the best water quality, pond environment and nutrition if we want our koi to thrive. Our koi are the products of the environment in which they live – so the better we can make the inputs, the better the outputs and overall condition of our koi.

Besides water quality, koi nutrition has the greatest effect on how koi perform in our ponds. Also, the food we offer our koi can also affect the water quality either directly through leaching or indirectly by how effectively our koi can digest the food. The food that we offer our koi (and pond system) can be regarded as our choice of operating system in the same way that the software that is installed to operate the hardware of a PC. It will determine how most aspects of your system function, particularly dictating how your koi perform. Just as ‘garbage in – garbage out’ is true for PCs, it equally applies to koi food and what we can hope to achieve by feeding it.

Why are there different koi foods?

Being cold-blooded and ‘slaves’ to their environment, just as koi activity and behaviour changes through the season, so do their nutritional requirements. The range of foods reflects:

  1. The range of nutritional requirements that koi have through the seasons (ie summer growth, autumn maintenance etc)
  2. The koi keeper’s wants and needs. For example, one koi keeper may opt to feed a colour enhancing food in the summer while another may choose to feed a staple food.
  3. Physical nature of food. Koi and pond foods are available in pellet, stick and mixed varieties depending on the size and range of koi and the feeding preferences of the different koi keepers.


Box Out: Koi Food Plus

Koi food can be regarded as a Trojan Horse, where the horse is the basic, complete diet and the soldiers hiding inside are any number of different supplements that boost aspects of our koi’s health, growth or colour.

  • Colour enhancers. The inclusion of specific carotenoid-rich ingredients will enhance the colour of koi.
  • Immunostimulants. These largely natural supplements boost a koi’s ability to resist and fight infection.
  • Stabilised Vitamin C. A heat-resistant Vitamin C is included to ensure that every mouthful of koi food offers them complete and balanced nutrition.


Should I change my koi’s diet at different times of year?

In summer when koi are growing at their fastest rate, they should be offered a high (37%+) protein diet that will fuel their growth. At these higher temperatures, koi are  able to digest their food efficiently resulting in good food conversion rates and less waste. They will also eat more food at this time of the year compared to any other.

At cooler temperatures (in spring and autumn), koi do not require the same raw materials (protein) for growth and cannot digest or take up the same quantities of food as they can in the summer. Consequently, koi should be fed a lower protein food in smaller quantities largely for the pond’s benefit. Arguably we could offer our koi a growth food in autumn and it would not adversely affect our koi (that would only partially digest it). However, the excessive waste element from feeding a growth food at cooler temperatures would seriously jeopardise our pond’s water quality. This is why we traditionally offer a lower protein, wheatgerm-based food at these temperatures. This means that koi can digest it relatively easily, but also means the pollution potential for the pond is reduced. In short – feeding a low protein food in the spring and autumn is better for your filter, and better for your fish.

Should I stop feeding altogether in winter?

If your pond follows normal outdoor ambient temperatures then from about October – February (global warming permitting), your koi will not feed as they will be colder than 8C. Don’t be concerned with the lengthy period over which your koi will not feed as this period of winter inactivity is simply natural and arguably necessary to maintain a pond full of healthy koi.

What are the best ways of ensuring that my koi get a balanced diet through the year?

Always check that the food you are offering your koi:

  1. Offers your koi a complete and balanced diet, which means declaring a Vitamin C content on the label.
  2. Does not spend too long on the pond’s surface, leaching out nutrients. Feed an a little and often basis.
  3. Is well within its best-before-date



Feeding Timeline (See graph)

Zone 1.

Pond temperature less than 8C. Do not feed because fish are inactive and have no appetite. Any food offered will not be eaten and will adversely affect the water quality.

Zone 2.

Pond temperature 8-14C. Offer a low protein, highly digestible ‘Wheatgerm’ diet in low quantities. Fish have a reduced metabolism and appetite at these temperatures and cannot utilise high levels of protein. A low protein food is offered to help preserve a good water quality.

Zone 3.

Temperature >14C. The growth phase.

Koi are growing at their fastest rate and can utilise a high protein diet. If a low protein diet was offered at these temperatures then you will not be capitalising on your koi’s growth potential. Ensure that filtration is in working order as there is the potential for large volumes of nitrogen-rich waste.

Kill blanketweed and string algae.