What Fish Can Live With Koi In A Tank?

What fish can live with koi in a tank?Community tanks are a beautiful way to connect to different varieties of fish and how a natural ecosystem interacts, but it can be difficult to combine fish that have restrictive environment requirements.

What fish can live with koi in a tank? The types of fish that can live with koi depend entirely if you have an indoor tank or if your koi are outside in a pond type environment. Not all commercially bought fish do well outside.

You must also consider the natural environment that your fish is from and how they will be affected by the climate in which you live.

A lot of factors go into picking compatible fish to live with your koi such as size and temperament, but don’t worry we can help you out with the basics.

Read further to get an understanding of the koi’s personality, factors you need to consider before adding fish to a koi tank, and last but not least which fish are compatible with koi.

Details of the Koi

The koi due to their beauty and personality have a large devoted following. Initially taking care of koi is a little daunting, changing feeding schedules and environment can be difficult to handle.

But after a while you will get used to their schedule their disposition will win you over.

There are hundreds of varieties of Koi. They are a subspecies carp that has been breed from the Japanese Amur carp who is crossbreed with other carp species for coloring.

Koi are categorized by their markings and scale pattern rather than personality, Some, such as the tea-stained Chagoi, who makes up for their muted coloring with a sweet nature.

Koi will revert to their Amur coloring after a few generations if they are not selectively breeding.

All Koi range on the larger size, but the exact size depends on the particular koi that you purchase.

  • Your common domesticated Koi will be between 12-15 inches long
  • Japanese Koi are 22-26 inches long
  • Jumbo-sized Koi get up to 34-36 inches long

Koi are not naturally an aggressive fish, not any more than any other fish that is. They still need their own space, plenty of food, and will get testy during mating time.

The Koi does have teeth, but they are so far back that you are not in danger of being bitten. The koi’s teeth are actually in their throat rather than their mouths.

They do have powerful mouths and can suction your finger if you take to long to give them a turn of food. This also plays a part with other fish, they can suck up another fish’s tail to the point where it reaches their back choppers and rips it off.

They will eat fry and other tiny water creatures or insects. They don’t typically eat smaller fish, but in the right circumstances, they will.

The majority of fish align with the pecking order, meaning that the bigger fish rule the roost while the smaller ones fall in line. The koi being a relatively large fish is going to rule the roost.

The koi are known to have very distinct personalities from fish to fish. Meaning that even though they are not thought of as aggressive fish you might find an aggressive individual.fish that do well with koi

When looking for tank mates’ size, environment, and personality all need to be considered

Community tanks are great, but you can’t just combine any fish that you like and expect them to live peacefully together. If your main focus is fish that are compatible with koi you have to consider their particular attributes and match them in other fish.

Picking fish that are of a similar size, environment, and the overall personality will help you a lot in the long run


While the fish is not known as an aggressive fish, fish as a whole have a natural pecking order which can’t be ignored. Bigger fish will pick on or eat smaller fish, there is nothing that you can do about that, it is just in their nature.

The easiest method to prevent fighting is to get fish that are either compatible due to species or are near the same size. The temperament of each fish variety should be considered, also, when stacking your pond.

While koi are not aggressive fish they are one that has big personalities that differ from each individual. So some koi that you come across will be docile and friendly while others will be one aggressive and pushy towards their other pond mates.

We show you in detail what the minimum tank size for koi is in this article!


Overall the koi is a friendly fish and needs other fish that are the same. If you introduce an aggressive species then the koi will start to get picked on especially the more amicable varieties.

Avoid aggressive fish that are larger than your koi, or just larger fish in general because they tend to be more aggressive.


You want all of your fish to be comfortable and part of that process is making sure that all of the fish that you get are compatible in the same environment.

The koi is a cold-water fish coming from chillier climates such as China and Japan, with some varieties breed with the common carp from Europe. Keeping koi in the same tank or pond as tropical fish doesn’t work because they are from completely different environments.

Other qualities to look for

Stacking your tank

Naturally, Koi are bottom-feeding fish, however, in captivity, they will come to the surface to be feed by you. Bottom-dwelling fish are typically scavengers who feed on the leftovers from other animals or any other morsels that they can find.

Statically stacking correctly will make your tank look better. Preventing the decay from the food to dirty the water that your fish live in.

Instead of fish crowded in one area of your tank, they will be at the bottom, middle and top making it look like you have more fish than you do. Besides astatic stacking, the tank correctly creates space for each variety of fish so they don’t feel like they are overcrowded.

No matter how docile your fish are they like their own space, stacking creates that for them. Another reason to consider the area in which your fish will live is cleanliness.compatible fish with koi

As boring as it sounds you need to create the full feeding process of a natural environment in this artificial setting. That means that some fish eat at the top, but tend to be sloppy and not eat all of the food that they are given.

With only top and middle fish that means there is a lot of uneaten food at the bottom of your pond. Uneaten food will decay at the bottom of your tank causing algae, lack of oxygen and a harder time for your pump to keep clean.

While a pump and filter will help clean out your water and put oxygen back in it helps to be mindful of your koi’s natural process so you can keep your tank or pond at it’s cleanest.

One thing that will help is to get bottom-dwelling fish in the pond with your koi fish. So all of the food that your koi doesn’t eat will be gobbled up by these natural cleaners.

Slow to grow and breed

Look for fish that are slow to grow instead of those that seem to grow big when your back is turned. Koi is a long-lived fish that take about 3-4 years to age. They will continue to grow in size after this period but at a much slower pace.

Fish that reach a larger size than your koi before that time will show aggression on the baby koi. It’s easier to purchase fish that have a similar growth period or who will not torture your koi when they are a fry.

You also don’t want fish that will produce a lot of fry. Even the smaller koi need a lot of room, with a fast-breeding fish the pond or tank will quickly become overtaken and possibly eaten by your koi.

Unless you have the set up to remove the baby fish your tank will become overcrowded. Which will lead to added waste in the tank, competition for space, and a lack of oxygen for everyone to breath.

Oxygen is very important to the koi fish, without it they will get stressed, which will cause their immune system to crash allowing parasites and bacteria to infiltrate their bodies or they will suffocate then die.

Tank or pond?

While we traditionally think of koi as a pond fish, they are compatible with tanks you just have to have a large tank and even larger if you want a community aquarium. Koi by themselves need at least a 1000 gallon tank to accommodate their size.

If they are of the bigger variety such as jumbo koi then they will need a much larger tank. Then if you are adding more fish into the tank it will have to be even larger.

For this reason, most people who have koi set up ponds instead of keeping them in a tank indoors. Each one has its good points and drawbacks.

With an indoor tank, you can control the temperature a lot better, but most people don’t have space or the money to house a massive tank. You need at least 50 gallons per koi in a tank.

That means if you have 5 koi you need a 250-gallon tank.

This is just for koi alone, adding additional fish means getting a bigger aquarium. Also since they are not in a pond your options for other fish in a community tank are expanded, in tanks you can house tropical fish with koi since the temperature can be regulated easier.

If you want to house your koi in an indoor tank then opt for the smaller koi instead of the jumbo size. People who keep koi in inside tanks are those who live without yard space or chillier areas where the fish would be in hibernation year round if they were kept outside.

Ponds make it much easier for you to provide the size that they need, all that you have to do is dig a larger hole for them to live. However, the temperature is not controllable so you will have to consider the climate where you live and how much to feed them.

It also limits your options for additional fish to those who work well in your climatic zone and a pond environment. If you can afford it a pond heater will help with temperature issues, especially during the colder months.

While the koi is a bottom-dwelling fish they frequently come to the surface to feed. In a pond, a lot of bottom-dwellers will kick up the dirt in your pond causing it to be murky. Limit the number of bottom-dwellers to help keep your pond clear.

Types of fish that do well with Koi

Compatible fish for koi depends on where you are keeping them. If you have a tank setup there are more options for different varieties of fish since you have a firmer grasp on the temperature.

Tropical fish are an option with koi tanks because of this very reason. However, if you have a pond for your koi you have to make sure that they are compatible with koi, pond living, and the climate where you live.

Before getting any fish to live with your koi in a pond talk to your local pet store or your fish dealer to see what types of fish work where you live.


  • Barbels
  • Golden Orfe
  • Golden Tench
  • Goldfish
  • Barbs
  • Catfish

Barbel fish are a type of carp native to Europe. They have similar needs and temperament to the koi fish and can live in both a tank or pond. These fish can get quite big, some can grow to be 4 feet.

The majority however only reach 40 inches. These fish work best with the jumbo variety of koi. Since they are slightly larger than the koi introduce them to when they are adults.

The Golden Orfe is a beautiful fish that reaches up 20 inches perfect for the medium-sized koi. They prefer to live in groups of their kind so do better with at least three fish. These fish can be housed in a tank, but due to their size, it’s best to keep them in a large pond.

Also called the doctor fish the Golden Tench makes your pond clearer because they eat the waste from other fish. Gross, but necessary. They can grow between 16 to 26 inches, so these work well with the medium-sized koi.

These are better in ponds rather than tanks due to size and their habit of settling in the mud at the bottom of their environment.

The koi is a type of carp so they do well with those of the same species and size. Traditionally goldfish are housed with koi. The beauty of it is obvious why, but also be selective with which type of goldfish and koi that you bring together.

You want the goldfish to match the same size of your koi fish otherwise your goldfish will be picked on. Koi will even suck in the goldfish’s fins and pull them off. Goldfish work in both tank and pond environments.

Barbs come in a variety of shapes and colors, for koi tanks, it’s best to purchase the larger type such as the Rosy Barb which can reach 6 inches. These work well in a tank environment. They are a docile fish so they will get along well with the smaller koi types.

Though catfish are a bit territorial they work well with koi of the same size in a tank. There are many varieties from small to large so make sure to get one that equals the size of your koi and introduce them when your koi are fully grown.

They are tropical fish but work well in different environments. They do tend to mess up the bottom of the tank at times so if that is a deal-breaker skip this fish.

Picking compatible fish is a tedious process. Finding fish that work well with your koi and their environment while also adding beauty might seem impossible, but thankfully it isn’t when you have a better understanding of koi and what their needs are.

If you look for species that are similar to the koi in temperament, size, and environment it will make the process a lot easier. Also fish do well with those who are in the same family as they are.

Patience and thoughtfulness will help make introducing your koi to new fish a lot easier.

But just in case keep a separate container for those times when fish turn out to be less compatible than you thought and keep a good relationship with your local fish dealer to get help for your specific area.

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