How to Take Care of Koi Fish

August 11, 2022

fish swimming at top of koipond

Koi fish can liven up your garden pond with their bright colors and friendly personality. They are super easy to care for but require an optimal environment to thrive. Here, we teach you the essentials of caring for Koi, so you can feel empowered to start your Koi fish pond today.

Get to Know Koi Fish

Koi fish are a colored variety of the Amur carp Cyprinus rubrofuscus, originally from Asia. Breeding and caring for colorful carp started in the 19th century in Japan. Rice farmers would catch, keep, and breed wild Koi to fertilize their rice gardens.

Over the years, Japanese Koi fish have been bred as ornamental fish for their bold colors. Today, they are a popular choice for garden ponds and can go on to live for 25-35 years. Some have been known to reach well over 100 years of age.

Koi fish come in various colors, patterns, sizes, and scale types. There are over 100 different Koi varieties. They are considered one of the most beautiful garden pond fish. However, keeping Koi fish requires great care and maintenance.

Koi fish can grow to between 24-36 inches and require a minimum tank size of 250 gallons per fish to avoid overcrowding.

Types of Koi Fish

four fish swimming in koi pond

Liven up your water garden with different types of Koi fish, each with its own distinctive coloration, patterns, and scales. Generally, they are found in yellow, black, blue, white, red, cream, and orange colors.

Koi fish can reach up to 3 feet long and are considered one of the biggest backyard fish. Generally, they are plump and have a round snout, a couple of barbels used for taste on the bottom and top of their mouth, no stomach, and a toothless jaw to suck up food and prey.

Female Koi tend to have a bigger and rounder body, while male Koi will have a more slender body. Males also tend to have more pointed fins that are colorful and opaque. Female Koi have rounded fins that are more semi or fully translucent.

If you are interested in having a varied Koi fish pond, consider these Koi fish types.

Butterfly Koi

Butterfly Koi, also known as Dragon Koi, is among the most popular varieties. They get their name from their long caudal and pectoral fins, an inherited trait from their goldfish ancestors.

The Kumonryu variant of this fish has black and white markings that can change through the seasons.

Kohaku Koi

The Kohaku Koi is the standard Koi variety distinguished by its white body and red markings. Young Kohaku has a translucent or pinkish appearance.

Taisho Sanke

Also known as Sanke, this Koi has a creamy white body with white and black markings and is one of the three main Koi types, including Showa and Kohaku.

Showa Sanshoku

Showa Sanshoku Koi looks very similar to Sanke Koi in its red, white, and black coloring. In Showa Sanshoku varieties, black is the dominant color and features white and red patterns.

Showa Koi can be divided into different types, including Kindai Showa, a Koi with a dominant white color, and Kin Showa, a Koi with radiant gold scales.


The Hikarimono Koi, also known as the Ogon Koi, differs from other varieties in that it only displays one color. Hikarimono Koi can be red, yellow, orange, cream, and platinum.


The Kawarimono variety encompasses 14 different types of Koi, including Kumonryu, Chagoi, Karasu, Kigoi, and Beni Matsukawabakke Koi. Essentially, it’s a descriptor for nonmetallic Koi and can be single-colored with white and red-tipped fins, black, or other colors like the green-colored Midorigoi Koi.

Koi Fish Equipment

Setting up a Koi fish habitat in your backyard is possible on a budget. Ultimately, your goal is to mimic its natural environment.

Koi fish can run you between $20 to $80 from an aquarium or pond supplier. However, if you want a special variety, you can buy them from breeders. They are typically more expensive and range between $200 or well over $1,000 for rare types.

Here is some equipment you will need to care for Koi:

  • Pond (at least 250 gallons of water per fish)
  • Netting to cover the pond
  • Small pump and filter
  • Air pump
  • Pond skimmer
  • Water thermometer
  • Water test kit for ammonia, nitrates, pH, and salt
  • Pond salt

API Pond Pond Water Salt, 4.4-Lbs.

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  • UV clarifier (optional)

API Pond Simply Clear Pond Water Clarifier, 16-oz.

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  • Pond heater (optional)

Koi Fish Behavior

Generally, healthy and happy Koi fish are relatively relaxed and happy aquatic creatures. Some may like to be pet, while others may prefer little human interaction. They are also known for having excellent memories and recognizing their owners.

Their behavior can be influenced by the season and water quality. Normal Koi can be seen happily swimming around the pond. They push their heads to the surface when fed. They tend to be more energetic in mild to warm weather.

When the sun goes down, they tend to stick together to rest. They may also forage for food or prey, although they are not as active at night.

Checking in on your Koi every day is the best way to determine if their behavior seems normal or out of the ordinary.

Aquatic Companions for Koi

Group of koi fish in pond

Keeping other fish or aquatic life with Koi is a great idea. Koi are peaceful creatures that can live in harmony with other aquatic life forms. If you are looking to spice up your garden pond’s biodiversity, consider adding these aquatic companions to your garden pond.

  • Goldfish
  • Orfe
  • Largemouth bass
  • Chinese high-fin banded shark
  • Trapdoor snail
  • Golden tench
  • Grass carp
  • Suckermouth catfish
  • Redear sunfish

Koi Fish Habitat

Above water shot of koi fish in pond

In the wild, the common carp ancestor, native to Asia and Europe, can be found in streams, lakes, and ponds with a low to minimum flow and a soft and muddy bottom. Carp can be found in tropical and temperate locations with temperatures above 70º F.

Koi can thrive in natural ponds and aquariums but prefer ponds. Koi ponds give them enough space to swim, forage, and lay thousands of eggs during mating season. Overcrowding can lead to aggression.

A deep enough pond should be between 3 to 4 feet deep. This depth can protect your fish from predators above, giving them a space to hide below. Netting over the pond can provide even more predator protection.

Another thing to consider is the bottom of your pond. Avoid having a rocky or hard gravel bottom since Koi like to swim and forage for food on the bottom or hide down there when it gets too cold. A rough bottom can cause injury. Make sure you have a fine gravel or smooth bottom in your pond.

Pond Size

Install a pond big enough to accommodate all your fish without getting overcrowded. Koi like to have enough swimming space and can become aggressive in crowded spaces. Keep in mind that adult Koi grow large and need plenty of room.

Small Koi ponds can have about 500 gallons of water, but the average pond has about 1,500 gallons. The Koi pond depth should be about 3-4 feet. The average pond can accommodate about 4-5 Koi.

Water Temperature

Koi prefer cold water, preferably temperatures 59-77º F. In the winter, when temperatures go way below their optimal temperatures, feed your Koi less than normal, about 2-3 times per week. If the temperature goes below 41º F, they will enter hibernation, and their digestive system stops.

Water Quality

A critical factor in the health of your Koi will be the quality of the water they’re swimming and eating in. Unhealthy water can be lethal to Koi. Essentially, you want pond water that is clean and well aerated.

If you’re filling up your garden pond with tap water, remove chlorine. The water’s pH should be between 7 to 7.5. Going outside this pH range can cause detrimental effects on your fish’s health

About 10-20% of the Koi fish water should ideally be replaced every week.

Pond Filter

One of the best things you can do to keep your pond clean is to install a water filtration system. Mechanical filtration can be used to physically remove any vegetation, insects, and other debris. Biological filtration uses beneficial bacteria to eliminate harmful chemicals from the water.

Mechanical filters should be cleaned regularly to avoid spreading bacteria and disease to your fish. A pond skimmer works on the surface of the water and can be paired with your biological system for the best filtration.

Oxygen Levels

Aeration in your pond is critical for optimal Koi health. Your fish need the right gas exchange and oxygen to live, eat, and breed. Ideally, your pond should have about 8 milligrams per liter of dissolved oxygen level in water of about 77º F.

Aquatic plants can affect your pond’s oxygen levels since they can consume the oxygen and exhale carbon dioxide at night. Providing the proper form of aeration to offset any oxygen depletion can maintain adequate oxygen levels in your pond.

Since warm water holds less oxygen, you’ll need to watch your oxygen levels in hot weather. Keep your pond near a shaded area or use aquatic plants like lily pads to reduce high temperatures, especially during the summer.

Regularly assess the oxygen levels and make adjustments if needed. We recommend using aeration equipment like bubbling devices to increase oxygen levels. Finally, remove any debris from your pond to reduce contamination. For example, decomposing algae can take up oxygen.

Ammonia, Nitrates, and Nitrites

If there’s one thing you should watch out for its nitrates, nitrites, and ammonia, which can be lethal for Koi.


Ammonia is toxic when it reaches 0.25 parts per million (ppm). We recommend having 0.0 parts per million of ammonia.

You may notice signs of high ammonia levels when your fish appears listless. Other symptoms include isolation, burns on gills and fins, loss of appetite, excess coat of mucous slime, and clamped fins.

To remove ammonia from your Koi pond, enlist the help of beneficial bacteria and change out about 25% of the pond water.

Nitrites and Nitrates

Compared to ammonia, nitrites and nitrates aren’t as toxic, but they can also have harmful effects on Koi and even cause death if you don’t take care of contamination quickly.

Signs of high nitrates in your Koi pond include brown-blood disease, which prevents the fish from getting enough oxygen from the water and can cause suffocation.

The ideal nitrate levels should be between 20 to 60 ppm. Anything over 80 ppm is at a dangerous level. The safest level is 0.00 ppm nitrates. Excess nitrates can cause damage to a fish’s immune and reproductive system.

Remove nitrates and nitrites by introducing helpful bacteria to restore a balance. Make sure your pond is adequately aerated and change your water partially to remove these contaminants.

Aquatic Plants for Koi

fish and lily pads in koi pond

Aquatic plants will not only improve the look of your pond and provide an outdoor relaxing space but also can be beneficial for your fish.

Aquatic plants can improve oxygen production and aeration, improve pH, and reduce ammonia levels that can be toxic to fish. In addition, they can help prevent the spread of algae by reducing the photosynthesis process.

Keep in mind that Koi have a big appetite, so they may want to feed on your aquatic plants. Avoid keeping plants toxic to fish or practice other strategies to keep your plants safe.

Here are a few aquatic plants to consider:

  • Water Lily
  • Eelgrass
  • Water Lettuce
  • Water Lotus
  • Water Hyacinth
  • Water Smartweed
  • Scouring Rush

If you’ll be introducing plants to your Koi pond consider these tips:

Install a vegetative filter when keeping your plants in a separate area from the main pond area where your fish swim. Natural filters can include sweet potato plants, water celery, umbrella palm, and water hyacinth.

Install plant shelves in your pond to keep your aquatic plants. Just remember that different water plants require different depths. For example, water lilies need depths of 12 to 36 inches of water.


Man feeding koi fish in koi pond

Koi fish need a balanced diet to achieve optimum health. Since they are omnivores, they can eat meat and plants and have a voracious appetite. Ideally, they should be fed about 2-3 times per day.

Feeding schedules can vary by season. For example, they may need more carbohydrates in the fall to prepare for winter. In the spring, they will want additional protein. In the winter, they will hibernate in the bottom of the pond.

Their primary diet should be commercial Koi feed in flake, pellet, or bar form. Flakes are optimal for small Koi, while bars are perfect for your bigger Koi. Floating pellets are the most entertaining to watch and preferred by Koi compared to sinking food that may be harder to find.

Koi food is primarily made from fish meal, squid meal, whitefish, shrimp meal, anchovy meal, blood meal, or herring meal. Secondary ingredients include corn gluten, soybean meal, and wheat germ.

The type of Koi food you give them can depend on their stage of life. For example, young Koi fish require a higher protein concentration in their diet compared to adult Koi. Koi fish need about 32-36% protein content, 3-9% fat content, low phosphorus levels, and vitamins A, C, D, E, and K.

Mazuri Koi Pond Nuggets 20 lb.

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We recommend providing them with various food types to prevent boredom. Treats can make up a small portion of their diet to avoid nutrient dilution.

Treats include vegetables, fruit, and other treats like hard-boiled eggs, unsalted cooked pasta or rice, and whole wheat bread. Commercial treats include black mosquito larvae, silkworm pupae, earthworms, bloodworms, tubifex worms, tadpoles, and wax moth larvae.

Avoid feeding your fish corn, white bread, frogs, peas, or wild bugs and fish you caught.

Avoid overfeeding your Koi fish, which can lead to negative health effects such as weight gain and contaminated water since the food waste will accumulate at the bottom of the pond. For best results, only feed them what they can eat in 5 minutes and if there’s any excess, feed them a little less next time.


Koi fish are prolific breeders, breeding thousands of eggs in a single season. Some will not hatch, and most don’t survive since larger fishes in the pond may eat them. Once the eggs are fertilized, baby koi settle along the bottom of the pond and hide in the pond plants until they are ready to come out and forage for food.

Koi Fish Health

What once were lively and happy fishes can become isolated and tired due to various diseases. Common culprits of poor fish health include poor water quality, overcrowding, and other environmental factors. Some common signs of poor fish health are reduced energy, gasping, isolation, ragged fins, ulcers, and more.

FAQs About Caring for Koi Fish

People petting koi fish

Are Koi Fish Easy to Take Care of?

Yes! They are relatively easy to care for. If you’re a complete beginner, maintaining optimal aeration, pH levels, and cleanliness can have a learning curve.

Although caring for Koi can have some high maintenance aspects, once you get the hang of it, caring for these creatures can be simple and rewarding.

Why are Koi Fish So Expensive?

Koi fish cost around $3,000 per year to keep and are generally more expensive to care for than dogs or cats. The cost is attributed to basic supply and demand economics. While Koi fish lay close to 100 thousand eggs in a breeding season, only about 60% of them hatch. From there, they are aggressively culled and selected by Koi farmers for preferable pattern, body shape, and to eliminate deformities or abnormalities. This leaves very few sellable specimens to meet demand.

How Long Do Koi Fish Live?

Koi fish can live for 25-35 years on average.

How Much Do Koi Fish Eat?

In captivity, Koi fish usually eat between 1-4% of their body weight per day.

Start your Koi Pond Today!

Are you ready to welcome Koi fish to your family? Keep your fish pond healthy with Wilco Farm Stores. We offer a wide selection of pond care and koi feed products. If you want to practice proper Koi fish care, trust the experts at Wilco Farm Stores.