Koi Food and Diets

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 colour 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.

NB No mammalian meats are permitted in koi diets in the EC through the BSE legislation!

* 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.

Choosing a Quality Koi Food

All reputable koi foods are formulated to provide balanced nutrition for koi and other pond fish. However, there is no strict industry-wide standard that a koi food must meet before it can be sold. For this reason, it is wise to be selective and informed when choosing a brand.

A little detective work goes a long way. Observe which foods are popular in aquatic stores, and ask fellow koi keepers or retailers what they personally use and recommend. First-hand experience often provides valuable insight.

When comparing foods, consider the following factors, which often distinguish premium brands and may be reflected in the price.

1. Value for Money

Compare weights carefully, not just bag size. Some pellets are more heavily expanded during extrusion, meaning they contain more air. A larger-looking bag may not necessarily contain more nutrition. Always compare cost per kilogram rather than judging by packaging volume alone.

2. Ingredient Quality and Additives

Examine the ingredient list. A wide range of high-quality raw materials generally indicates a more complete and carefully formulated diet.

Look for beneficial additives such as:

Colour enhancers. Natural ingredients like spirulina, krill and chrysanthemum meal, along with compounds such as astaxanthin and canthaxanthin, are commonly included to enhance skin colouration. Foods containing these additives can improve colour intensity but will usually cost more.

Stabilised Vitamin C. Much of the natural vitamin C content can be lost during processing. Stabilised vitamin C is added to ensure koi receive sufficient levels of this essential nutrient, supporting immune function and overall health.

3. Packaging Quality

Good packaging protects feed quality. Ideally, food should be supplied in robust, resealable bags to maintain freshness. Exposure to air, moisture and light can rapidly degrade vitamins and fats, reducing nutritional value.

4. Best Before Date

Always check the best before date and ensure you are purchasing fresh stock. Ideally, the date should extend through the remainder of the feeding season. Vitamin levels are typically guaranteed for up to 12 months after manufacture, but nutritional quality declines over time. The closer the product is to its expiry date, the less fresh it is likely to be.

By comparing these factors — formulation, additives, packaging and freshness — you can select a food that supports both koi health and good water quality while offering genuine value for money.

Use the labels below as a guide for what to look for when choosing a koi food and never be afraid to ask a retailer what food they use and recommend. 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 ‘belt and braces’ diets which are not significantly better than mid-priced well balanced diets. Now that you know what to look for when choosing a suitable koi diet, best of luck!