Fruits, vegetables, insects: the treats your koi love (and those that make them sick)

Holding out a slice of watermelon and watching a large koi come and bite it from your hand is one of the pleasures of pond ownership. Koi carp are omnivorous and curious, and varying their diet is good for them. Provided you follow three rules: treats must remain treats, foods must be suited to their digestive system, and the water must be warm enough for them to digest them. Here is the complete list, tested in our own ponds.

What a koi really eats

In the wild, the common carp searches the bottom for larvae, worms, small crustaceans, seeds, and tender plants. Koi have retained this omnivorous diet. They do not have a stomach in the strict sense: their food passes directly into a long intestine, which digests proteins and tender plants well, but digests raw starches and animal fats poorly.

Two practical consequences follow. First, it eats little at a time but often. Second, its digestion depends entirely on the water temperature: below 12-15 °C, everything slows down, and difficult-to-digest food may ferment in the intestine.

Approved vegetables and fruits

Always wash fruits and vegetables to remove pesticide residues, and cut them into pieces smaller than the mouths of your smallest fish.

Live proteins: worms, shrimp and insects

This is the treat closest to their natural diet, and the one that generates the most enthusiasm.

• Earthworms from your garden (untreated), rinsed and cut up for medium-sized fish.
• Shelled shrimp, raw and unseasoned, or small dried shrimp.
• Dried gammarus, rich in carotenoids.
• Silkworm pupae: the traditional treat of Japanese breeders, very rich.
• Black soldier fly larvae: an excellent nutritional profile, increasingly used.

The right time for insects: from late spring to early autumn, when the water stays above 18 °C. This is the growth period, when koi need protein. In autumn, when the water temperature drops again, switch back to light foods, higher in wheat germ and lower in protein.

What you should never feed them

• Bread: it swells, ferments, clouds the water and provides almost nothing. It is the most common mistake.
• Dog and cat kibble: too fatty, it overloads the liver.
• Meat, deli meats, fatty fish: poorly digested fats and immediate water pollution.
• Raw corn, rice or pasta: indigestible starches.
• Any salted, sweetened, seasoned or processed food.
• Commercial fishing baits: sometimes high in additives and fat.

The four golden rules

1. 10% maximum of the ration. Complete food remains the foundation: it contains the vitamins, minerals and amino acid balance that no treat can provide on its own.
2. Water above 15 °C. No treats below that temperature.
3. Ten minutes, no more. Remove anything uneaten: a piece of fruit rotting at the bottom feeds algae.
4. New food = small amount. Introduce one food at a time and observe the droppings for two days.

Hand-feeding is also the best way to tame your koi and observe them up close: this is often how you spot an injury, a damaged fin or unusual behavior early.

Also read

How to choose good food for my koi carp?

READ THE ARTICLE

Frequently asked questions

— Can I give lettuce to my koi carp?

Yes, it is even one of the best treats. Choose romaine or oak leaf lettuce over iceberg lettuce, which is low in nutrients. A leaf held at the edge of the pond keeps them occupied for many minutes.

— Can koi eat bread?

No. Bread swells in the intestine, ferments, clouds the water, and provides nothing useful. It is the first thing to ban, especially when children feed the fish.

— When should I give insects to my koi?

In peak season, when the water remains above 18 °C, as a supplement to the usual food. Avoid them in early spring and autumn, when digestion slows down.

— Do treats improve colors?

Some contribute to this, such as amphipods or shrimp rich in carotenoids, but a color-enhancing food formulated with spirulina and astaxanthin remains much more effective and consistent.

In summary

• Yes: leafy greens, watermelon, orange, peas, zucchini, worms, shrimp, insects.
• No: bread, kibble, meat, raw starches, processed foods.
• 10% of the ration, with water above 15 °C, and leftovers removed after ten minutes.
• Complete food remains the basis of the diet.

Last updated: September 28, 2026.