Koi food functional ingredients

A koi food is formulated to satisfy many different demands – performing a host of different functions

  • Function 1:      Complete and balanced diet. A koi food must satisfy the basic nutritional needs of our koi, so that they are able to maintain their health and vitality, as well as grow.
  • Function 2:      Water Quality. A koi diet is formulated and engineered with the health and stability of the pond environment in mind. A poorly formulated food will not only not achieve the 1st function (above), but could also put all our koi at risk by what it could do to our water quality.
  • Function 3. Food Plus. This is what I describe as the ‘bells and whistles’. That is – an array of functional ingredients that can be added to a food to produce a beneficial response in our koi.


The ‘plus’ element of the koi diet is the part that is developed to provide koi keeper with a number of tangible benefits over and above those of fulfilling the basic nutritional needs of their koi. Functional koi nutrition uses the food as a vehicle by which it carries a number of additives that can enhance further the health, growth or colour of a koi.

By feeding our koi on an artificial food means that it offers us the benefit of complete flexibility in formulation. This provides koi food manufacturer with the opportunity to incorporate a new ingredient into a test diet at varying inclusion rates that can be verified and duplicated if necessary for research purposes. Furthermore, such additives can then be added in bulk runs with guaranteed inclusion rates, something that would just not be possible with a completely fresh diet. This also gives us the flexibility of incorporating ‘food plus’ or functional ingredients very precisely into every mouthful of a commercial koi food.

Functional Ingredients

1. Vitamin and Mineral Supplements

A koi food incorporates a blend of natural ingredients – ranging from fishmeal to cereals. These ingredients will bring with them to the diet all of the 5 nutrients: proteins, carbohydrates, lipids but may vary in their vitamin and mineral content. To guarantee that each pellet of food contains sufficient vitamins and minerals in the correct ratio and quantity, we can add a koi-specific vitamin and mineral premix. The inclusion of a vitamin and mineral premix will ensure that your koi will benefit from a complete and balanced diet. Some of these will be man-made additives (similar to vitamin or mineral supplements we might take) eg the heat-resistant Stabilised Vitamin C while others (particularly minerals) will be largely natural in origin.

Clay (high quality calcium montmorillonite) has been used successfully as a pond additive for many years, whereby it is added in a dry, powdered form on a regular basis. The minerals within the clay interact with the pond water to re-mineralise the ‘tired’ pond water with minerals that are so abundant and beneficial in a natural clay pond. Koi of course, compared to us, have the ability to source and absorb minerals from their environment, not relying solely on their diet for their mineral intake.

Clay can now be found within some koi foods so that koi can also benefit from ingesting it directly in their diet, something koi benefit from when grazing and rooting around in a mud pond. When clay is used as a pond additive and in food, the gap between the ideal conditions of a clay pond and that of a clear, highly filtered koi pond is closed. The inclusion of clay in a koi food is a significant departure from the ‘rocket fuel’ approach previously adopted in the formulation of koi foods, where the emphasis was placed on a highly digestible, low ash, low waste diet. The inclusion of clay in koi foods now recognises that a natural diet is not necessarily low waste, and that a low waste diet does not necessarily offer koi the best all round, longterm nutrition.   

2. Colour Enhancers

Colour enhancers were probably the first functional additives included in koi foods. Recognising that ornamental carp can utilise and manipulate a range of carotenoid pigments, natural pigment sources such as spirulina, krill and paprika have been incorporated into koi diets for many years. Some typical ingredients in a koi food (usually plant in origin) will contribute carotenoids to the diet, but the addition of specific colour enhancing ingredients ensures colour enhancement in koi is effective.  More recent research has identified the key pigments that fish incorporate into their tissues to enhance colour. Koi are able to synthesise these pigments from the array of carotenoids supplied in a natural source. Colour enhancement technology has now progressed to supplying koi with the specific carotenoids they require, in the form they can readily utilise. Consequently, faster-acting synthetic carotenoids such as astaxanthin and canthaxanthin (the concentrated pigments that are actually utilised by fish) appear in the formulation of koi foods.

3. Immunostimulants

The discovery of a range of compounds that can have an immunostimulatory effect on koi has lead to the inclusion of additional functional ingredients in their diets – enhancing and protecting koi health. Immunostimulants work in a number of ways to boost a koi’s ability to fight or protect itself from disease. Whenever we scratch or graze our skin, blood immediately gets to work to counter any foreign matter that may opportunistically enter the wound. These could range from viruses, bacteria or fungi, through to dead particulate material. Either way, these foreign bodies must be challenged by the body’s first line of defence which is the non-specific immune response. This involves the Pacman-like white blood cells that engulf and digest these foreign bodies. One group of immunostimulants acts to enhance the performance of these white blood cells, thus improving a koi’s response to disease.

Other immunostimulant additives have a different yet complimentary effect on invading organisms, particularly bacteria. One particular immunostimulant group has been shown to directly interfere with the ability of pathogenic bacteria to attach to fish tissues, preventing the onset of infection. Besides propolis (which is a beehive by-product) the majority of immunostimulants are either fungal or bacterial in origin, usually proving most effective when fed in rotation with a normal diet (i.e two weeks on, two weeks off).

Boxout:  Ash (to be placed near to the section on Vitamin and Mineral supplement)

Even though the ash content of a koi food must be declared on the pack’s analysis, it does not mean that ash is included as an ingredient in the diet. Ash simply refers to the percentage of the diet that is inorganic. That is, when 100g of a diet is burnt, what weight is left? This is then referred to as the ash content, which relates to the mineral content of the food. Minerals will unavoidably ‘piggy-back’ into the food with other ingredients – especially fishmeal which has a naturally high mineral content (see graph). The higher the fishmeal content, the higher the overall ash content of the diet – it’s unavoidable. So contrary to some comments that I’ve heard, ash is not added as a cheap bulking agent, nor can the quality of a food be deduced by its ash content.

Boxout: A typical vitamin and mineral premix.

Choline Chloride 

Vitamin A

Vitamin D3

Vitamin E

Alpha Tocopherol

Vitamin K

Vitamin B1

Vitamin B2

Vitamin B5

Vitamin B12

Pantothenic Acid

Nicotinic Acid


Folic Acid

Vitamin C

Inositol Copper










BoxOut: At a Glance:

Functional Ingredient Main Function Level
Stabilised Vitamin C Health and resistance to disease 300mg/Kg
Spirulina Colour Enhancement <1%
Propolis Immunostimulant <1%
Nishi-Guard Immunostimulant <1%
Nishi-Clay Mineral Source <1%


BoxOut: Feeding Treats

Natural foods that can be a source of functional ingredients.

1. Fresh fruit (oranges, banana)             Colour enhancers, Vitamins and minerals

2. Mussels, Prawns                               Colour enhancers, Vitamins and minerals

3. Fresh Vegetables (lettuce, tomato)    Colour enhancers, Vitamins and minerals

Boxout: Next Month

We turn detective and investigate koi food labels. What should we look for and how do we interpret the information on a label?

Kill blanketweed and string algae.