Koi and all other fish are just like us in that they have particular dietary requirements. Naturally, koi will scavenge and root around a pond bottom as an aquatic pig eating worms, algae and debris, but where they are stocked in an artificial garden pond their diet and overall health is reliant on what they are fed artificially.

As a close relative of the carp (they even share the same name Cyprinus carpio) the nutritional requirements are almost identical to that of carp and similar to ourselves in that they are omnivores, eating both plant and animal material. In fact, there is very little difference between the dietary requirements of koi and other pond fish such as goldfish, comets and shubunkins. Manufactured koi diets tend to be a little more refined than pond fish diets with a greater emphasis on protein content and color enhancement. Artificial koi diets can contain a wide range of raw materials in their formulation as long as they provide an overall balanced diet. Just think of the vast range of foods we can eat and still remain healthy. However, the blend of raw materials in a koi diet must satisfy specific criteria to provide sufficient of the following:

• Protein. Levels of approximately 30% are typical but will be higher if a growth food and lower than this if a low temperature food. Protein is present for growth and repair and is the diet’s most costly ingredient. Sources of protein include both animal and plant derivatives and meals such as fishmeal, soya, wheat and egg.
• Carbohydrate. These are the complex sugars such as starch and cellulose. They are all plant in origin and are included in high quantities in koi diets as a cheap source of energy. They are also included as a source of fibre to aid digestion.
• Oils. Oils are included as fish or vegetable oils. Usually less than 10% in the diet they are used by koi in the production of new tissues etc. If too much oil is included then pellets appear greasy and oily as in a trout pellet. These tend to be too rich for koi and can cause water quality problems.
• Vitamins and Minerals. Manufactured diets often rely on the natural vitamin and mineral content included in the raw ingredients. More recently better quality brands have been including stable supplements of the notoriously unstable Vitamin C.

All reputable koi foods will satisfy the above, providing adequate balanced nutrition for your koi and pondfish however there is no industry standard that koi food must meet before it can be sold. Carry out some detective work yourself before buying. Look at shop displays to spot which are the popular foods and ask friends and aquatic retailers which food they use or would recommend. When choosing a food it is also wise to keep an eye out for the following. These may often set brands apart and may be reflected in the price.

1. Value for money. Check and compare weights. This may sound obvious but rival brands may produce pellets that are more ‘blown’ with air than others. This may give the impression of getting a larger pack for your money when in fact you may be paying for air!

2. Look on the ingredient list for a wide range of ingredients and for beneficial additives such as:

Color enhancers. Raw ingredients such as spirulina, krill, chrysanthemum meal and other synthetic compounds such a astaxanthin and canthaxanthin are included to enhance the skin coloration in fish. A food containing these will improve your fish’s color but will also increase the price of the food.

Stabilized Vitamin C. Most of the natural Vitamin C is lost in the milling process. Stabilized Vitamin C is added to provide a boost of such an essential Vitamin ensuring your koi are kept in tip-top condition.

3. Packaging. Is the packaging robust and re-sealable enabling you to keep the food fresh for a reasonable period? If food is left open to the air then it’s quality will rapidly deteriorate.

4. Best before date. Make sure that you are buying this year’s stock and that the ‘Best Before’ date will last until the end of the season. Vitamin content should be present up to 12 months after manufacture. The less time there is on the best before date the less fresh the food is.

You may find it useful to ask your koi dealer what they feed their fish. They will be very well informed as to what they want from a food and will only offer their own koi what they consider to be the best for them. Be careful not to be too influenced by price as there are unbalanced ‘budget’ diets on the market. In the same way there are over-priced diets which are not significantly better than mid-priced well balanced diets.