A Complete Guide to Caring for Your Koi Fish

Are you wanting to decorate your backyard and make it seem more like an oasis? Adding a koi pond is a great way to do this. How do you take care of a koi fish though? What does that all entail?

Koi fish rarely live in a tank, because they require at least 250 gallons of water per fish. They live in schools of five to fifteen other fish, so having a pond is the best option for koi fish. They are omnivores and will eat plants and insects in their koi pond, making their care easy.

Okay, so you need a koi pond. How do you do that? What do you need to make a koi pond work? Keep reading and you will find out all that you need to know about koi fish and their habitat.

koi fish in the lotus pond

Koi Fish Basics

Koi fish are native to Japan and are directly related to goldfish. They typically live in outdoor garden ponds and can live up to fifty years. They can grow up to forty inches or more, depending on the breed. Also, koi fish can be kept inside large aquariums if you prefer that. You just have to have a very large tank.

To give you some quick info on the basics, we’ve compiled a table for you.

Scientific NameCyprinus rubrofuscus
Care LevelIntermediate
Water Conditions (Temp, pH, KH)74-86 degrees Fahrenheit

6-9 pH

1-10 KH
Max Size 40 inches or more (dependent of breed)
Minimum Habitat Size250 gallons
Average Cost (per)$50

There are a few different types of koi fish and they are usually different because of their looks.

  • Butterfly Koi: They are highly prized and valued. Their fins are longer than other koi fish.
  • Kohaku: White-skinned that have red marks on their head
  • Taisho Sanshoku: Similar in appearance to Kohaku Koi, but have small black markings as well as the red marks
  • Chagoi: Usually pale green or brown and are very calm creatures
  • Showa Sanshoku: Mostly black with red and white markings, commonly known as Showa in the US
  • Bekko: Red, yellow, or white, with black markings
  • Asagi: Light blue with red underbellies, that can also be light yellow or cream
  • Doitsu-koi: Crossbred and are more similar to carp
  • Tancho: Red patches on their heads
  • Goshiki: Usually red, but can also be black and pale blue

Koi fish are usually 1/16th of an inch when hatched, but will grow up to half of their final adult length at twenty-four months.

After two years, koi will grow slowly, tapering off between ten and fourteen years. It all depends on their environment, vitamin intake, and stress levels.


Koi fish are omnivores, meaning they eat vegetables and meat. In the wild, koi will not eat anything that will not eat them first.

They usually eat whatever is in their ponds, such as algae, plant material, zooplankton, and insects. Though they will not prey on other fish, they may eat their eggs. Since koi fish eat whatever is in their pond, it is important to replicate that environment to make sure your koi remain healthy.

Koi are usually fed with floating pellets, but also enjoy moderate amounts of live foods, such as bloodworms and river shrimp. You can also introduce water fleas, brine shrimp, and insects into the pond for more protein options for your koi.

Having a good stock of algae and floating weeds will prevent your koi from uprooting the plants in your water garden. Koi fish have a strange way of hunting for food. If food is not available, they will dig and burrow into the sediment of your pond and uproot the plants.

When you bring in commercial food, it should be high in protein.

If needed, you can also give your koi corn and rice as a supplement.

It is important to not overfeed your koi because they can easily become overweight. Also, it can lead to polluting the waters of your pond if they do not eat the food you give them.

Koi fish tend to eat more when the temperature is high in the water, so take note of that. You should only feed them what they can eat within five minutes, preventing them from over-eating or allowing access to float to the bottom of the pond. They may act hungry all the time, but it is important to their health to monitor their food consumption.

Vegetables such as lettuce, diced cabbage, duckweed, and aquatic plants are great options for koi. You can also feed them bread or cereals, but limit this and stick to mostly vegetables and protein to keep your koi healthy.

Habitat Setup

Koi fish are native to Europe and Asia and usually live in lakes, ponds, or streams with muddy bottoms and minimal water flow. They are most active during dusk and dawn but will swim all day long. Koi are coldwater fish and can survive in various conditions.

They were actually bred specifically for their coloration and have been kept in captivity ever since.

Instead of having a tank, koi fish need more space, so an outdoor or indoor pond is best for them. Koi fish can grow quite large and live for a long time. A pond is the best environment for them, especially since they live for such a long time.

Water Conditions

Koi prefer water temperatures above 70 degrees Fahrenheit (21 C). Their pond should be between 74-86 degrees Fahrenheit (23-30 C) all year round. To help in the colder months, a water heating system should be used.

It is important to have a filter that will work for a large pond to keep your pond safe and clean for the koi fish. You need to be diligent to make sure all waste is removed quickly to keep the water properly filtered.

A bottom drain is helpful because it allows for easy cleaning and water changes. The pond should be made of concrete with a rubber lining and muddy bottom. Fine gravel also works at the bottom of the pond. As long as the bottom is safe for koi to be around, it will be fine, as koi spend a lot of time near the bottom of the pond.

The pH of the water should be between 6-9 since koi prefer a natural pH. Having crushed limestone in the pond will help maintain the pH of the water. It is important to check the pH levels frequently.

Water flow is not necessary for koi to survive, but they will not mind if there is a stream or waterfall in their pond. Having a waterfall can even help your pond to be even more beautiful.

A pond should have at least 250 gallons of water, following the rule of thumb of having ten gallons of water per inch of a fully grown koi. There needs to be a minimum depth of six feet with shallow and deep areas. A large school of koi fish requires 1,000 gallons of water.

Another thing to note is that koi fish do not like direct sunlight. If your pond is outside, adding trees or brush to keep the sun out of the pond will make for happy and healthy koi fish.

Outdoor Water Garden

The best setup for your koi pond is to create an outdoor water garden. It ties together the koi pond with other beautiful features to enhance the pond.

The best way to do this is to add non-invasive plants such as:

  • Water hyacinth
  • Water lilies
  • Cattails
  • Pickerels
  • Floating pondweed
  • Duckweed

Here is a video that will give you an idea of how to build your own water garden.

Pond Mates

Having different types of animals in your pond makes for a fun environment. Koi get along well with a lot of other fish and adding in other ones can help them feel more at home.

There are several creatures that will be great pond mates for your koi fish.

  • Goldfish
  • Grass Carp
  • Sunfish
  • Catfish
  • Golden Orfe
  • Barbel
  • Golden Tench
  • Largemouth Bass
  • Striped Bass
  • Chinese Hi Fin Banded Shark
  • Trapdoor Snail
  • Frogs (note: it is best to attract local frogs rather than buying frogs to add to the ecosystem as they could have diseases)

While koi fish work well with much other fish, these fish should be avoided:

  • Bluegill
  • Small cyprinids (nano fish)
  • Channel Catfish
  • Bullhead Catfish
  • Crayfish
  • Most tropical fish

Keeping Your Koi Fish Healthy

Most diseases of koi come from poor water quality. By maintaining the proper temperature and pH and cleaning the tank often, you can prevent most diseases in your koi pond.

You can also be diligent about not overfeeding your koi, which will keep the water clear from leftover food. On top of this, a filter will help prevent this as well.

The most common diseases for koi fish are ich, parasites, anchor worms, fin rot, dropsy, and fish lice. Symptoms of these diseases are:

  • unusual swimming patterns
  • discolored fins
  • a change in appetite
  • lethargy
  • breathing difficulty

Another disease to look out for is called koi herpesvirus or KHV. KHV affects all types of carp and once infected, there is an 80% chance the koi will die. Symptoms of KHV are difficulty breathing, sunken eyes, and lesions at the gills.

Usually when one koi have KHV the whole population much be euthanized.

You can prevent KHV by carefully inspecting the health of each carp before adding it to the pond. New fish should be quarantined for two weeks before being added to the pond.

We hope our guide helps you on your way to having a happy and healthy koi fish environment.

If you like the article above, here are some other similar articles you should check out!

Can Koi fish eat human food?Opens in a new tab.

Red Tail Catfish care: Lifespan, Tank Mates, Diet, and HealthOpens in a new tab.

Peacock Bass care: : Lifespan, Tank Mates, Diet, and HealthOpens in a new tab.

Rick Kesler

I'm Rick and I've kept freshwater fish for over 5 years now. My main tank now is a 55-gallon tropical freshwater tank and my wife and I both just love watching all of our different fish while they swim around, some schooling and others not. I've also learned a lot about what to do and what not to do to keep our fish healthy and happy.

Recent Posts