What Do Koi Fish Eat? Everything You Need to Know

Koi originated as colorful, ornamental versions of the common carp (Cyprinus carpio), with roots in 4th-century China and early 19th-century Japan. Originally raised for food, farmers in Japan’s Niigata region began breeding them for color mutations, developing Nishikigoi (brocaded carp) as an ornamental pond fish. As a common pet, you might be wondering what koi fish eat, especially if you are considering some for your pond. Continue reading to learn about what koi eat and how they survive in the dead of winter.

What do koi fish eat?

Koi fish eat worms, larvae, seeds, algae, insects, and small crustaceans. Technically omnivores, koi will eat pretty much anything they can fit in their mouths. Koi don’t have teeth in their circular mouths, which makes it hard for them to bite or tear food. Instead, their fleshy mouths are designed for sucking in food.

Koi are known as benthic feeders. Benthic feeders live near the bottom of a body of water and subsist on what they find there. Commonly called bottom feeders, koi sweep the sediment bed of the water that they live in, searching for food. While they primarily eat from the bottom of sediment beds, modern domestication has allowed them to eat floating debris and food.

Since they have no teeth, many people feed koi food pellets with their bare hands. As the koi feed, they often suck on the person’s fingers, which can feel quite ticklish. You don’t have to worry about swimming or placing your hands in water where koi are present, as they aren’t harmful to humans.

When koi are introduced into wild habitats, they can be destructive because of their feeding habits. As they glide along the bottom of a waterway, they cause debris and sediment to loosen and unsettle. Known as turbidity, the unsettled sediment reduces light penetration and stops plants from taking root, often killing them. The increased sediment can make the water so cloudy that it becomes undrinkable for humans and animals.

Koi are sometimes found in human-made lakes and golf ponds, but their introduction is generally discouraged as they can damage plant life and disrupt local ecosystems.

A complete list of the foods koi fish eat:

Here is a list of the most common foods a koi will eat in a pond or natural environment:

• algae
• silkworm pupae
• bloodworms
• earthworms
• mosquito larvae
• tadpoles
• duckweed
• hyacinths

Although these are the most common foods that koi fish eat, they aren’t very picky about their diet.

Who Competes with Koi Fish for Food?

Since koi live in pond ecosystems, they constantly compete with other fish. In domesticated, human-made environments, koi don’t have many competitors because humans provide food in the form of pellets or feed.

In a wild environment, koi often live with other carp, killifish, and minnows, although they may eat them if they are small enough. They are also found with large fish commonly seen in lakes and streams, like catfish, bass, sunfish, or perch.

How Much do Koi Fish Eat?

Koi fish eat based upon the ambient water temperature. The colder the water, the less active they are. The warmer the water, the more active they are. In domesticated situations, koi will usually eat 1-4% of their body weight. In the wild, koi are always looking for food, sweeping the bottom and sucking up anything they come across.

For domesticated koi, it’s usually better to underfeed than overfeed, as overfeeding is more likely to cause health issues.

The ideal diet for koi generally contains 35-40% protein and 5-10% fat, depending on age and activity level. Be sure that any feed given to koi is low in phosphorus. Too much phosphorus in a pond ecosystem will promote unchecked algae growth and cause health problems to koi and any other fish in the pond.

What do koi fish eat in the different seasons?

Koi are poikilothermic, meaning they don’t have a natural ability to regulate their body temperature. As a result, their activity levels directly correlate to the ambient temperature of the water, in turn affecting their eating habits from season to season.

During warm seasons, when the water is between 71°F and 85°F, a high-protein diet is recommended because koi are more active, moving, and growing. Koi may eat up to four times a day during these warmer months.

During the cooler winter seasons, when the water is between 41°F and 60°F, a carbohydrate-based diet of wheat germ is recommended to provide long-term energy and help koi conserve resources.

When the temperature drops below 40°F, koi stop eating and enter a state of hibernation known as torpor. Torpor drastically reduces their energy needs, decreases their metabolism, and slows their bodily functions. This fantastic adaptation allows koi to live in places that get below freezing in the winter.

What do Captive Koi Eat?

Depending on their size, captive koi can eat store-bought flakes, pellets, or bars. Small koi will find it easier to eat flakes as they are the smallest. For medium to large koi, pellets are ideal. Bars are intended for the largest koi, who can eat them whole, but smaller koi will also try to nibble on them. Owners can give occasional treats. Things like soft fruits, vegetables, and whole grains are ideal. Never give your koi fish corn, uncooked rice (as it expands in their stomach), or white bread.