Can Koi Fish Live In A Tank? Read This!

Koi fish are popular fish due to their beauty and tranquillity, but not everyone who wants Koi fish has space for a Koi pond in their garden. This can be disappointing for some people and can lead people to look for alternative ways to keep Koi fish. So, Can Koi fish live in a tank?

Koi fish can live in a tank, but you will need to ensure the tank is big enough to house at least three Koi as they are social animals and need the company of their own kind. You also must ensure you keep the tank clean and in the perfect conditions for the Koi to thrive in your care.

What is the best tank size for Koi fish? What are the best ways to ensure your Koi fish are happy in their tank? How big do Koi fish get when kept in a tank? Let’s find out!

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Can Koi Fish Live In A Tank?

Koi fish are becoming popular as they bring a sense of calm to any location you keep them in, and with how busy the world is, most people want to have something that can bring some calm into their lives.

As Koi fish grow in popularity, more and more people are wondering if these fish can be kept indoors in a tank or can only be kept outdoors in a Koi pond. This is mainly due to most people not having the outdoor space to build a Koi pond of their own.

If this is the circumstance you are going through, there is some good news: Koi fish can be kept in a tank in your home. However, there are some restrictions to this, and you will need to ensure that your Koi fish have everything they require to live happy and healthy lives in the tank.

You need to ensure you have a tank big enough for your particular Koi fish as Koi fish are highly active and love swimming around. You need to know exactly how to care for them and what they need.

You will need some equipment to ensure the conditions in the tank are perfect for your Koi fish to thrive. A tank housing Koi fish will need constant monitoring to ensure the fish stay healthy. So, keeping Koi in a tank can be done, but they will require more care than being kept in a Koi pond outdoors.

What Is The Best Size Tank For Koi Fish?

One of the main concerns when placing Koi fish into a tank is the size of the tank, as Koi fish are large and require a lot of tank space to stay healthy. This means that the tank will also take up a large area in your home, so you must ensure you have room for it before filling it with Koi fish.

A standard Koi fish that is well-cared-for can grow 24 inches in length, while the larger Koi fish species can grow to 36 inches. These are massive fish, and they are active, meaning they need space to swim.

So, you need to ensure the size of your tank can hold the Koi fish when the fish is fully grown. Even though, as with most other fish, the growth of a Koi fish will be self-limited to the size of the tank you keep them in, it is better not to stunt your fish’s growth as this can be cruel and lead to some health complications later.

So, how big does your tank need to be to house a Koi fish comfortably? When looking at tank sizes for Koi fish, the general rule is 10 gallons per inch of the fish. So, a Koi fish that is 12 inches will require a tank that is 120 gallons for the fish to be healthy.

You need to keep in mind that this calculation doesn’t consider the girth of the Koi fish, so you might need a slightly bigger tank than your calculations. Below are the recommended tank sizes based on the Koi fish’s size:

  • A small Koi measuring between 2 and 8 inches requires a tank of 50 to 100 gallons.
  • A medium Koi fish measuring between 8 and 14 inches requires a tank of 100- 200 gallons.
  • A Large Koi measuring between 14 and 24 inches requires a 200-500 gallons tank.
  • A jumbo Koi that measures between 24 and 36 inches requires a tank of 500 to 900 gallons.

How To Keep Koi Happy In A Tank?

If you have the space for a tank that can house Koi fish in your home and you are up to the challenge of taking care of the Koi fish and have a tank big enough, you can keep Koi fish in a tank.

However, if you do this, there are a few things you need to know about caring for your Koi fish in the tank. As your Koi fish are your pets, you want them to live happy, healthy, and fulfilling lives, so you must ensure you provide them with the means to do this.

Let’s go through a few ways to ensure your Koi fish will be happy in the tank you provide them so they can thrive in your care.

Keep Water Conditions Constant

When you keep Koi fish in a tank, you will need to monitor the water conditions in the tank to ensure they are perfect for your Koi fish. Water conditions in the tank can change weekly, which can be drastic if you are not careful.

You need to have a filter set up in the tank to help keep the water clear of particles that could affect the health of your fish.

You need to ensure that the water has a constant oxygen level. The best way to ensure a high oxygen level in the water is by using a pump and placing some living plants in the tank with your fish.

Keep Koi Fish In The Same Tank Together

Two yellow koi fish in a fish tank

One thing you need to know about Koi fish is that where there is one Koi, there needs to be more. Koi fish are social fish and must be kept with other Koi fish to be happy. Koi fish feel the most comfortable and safe when they are in a school of Koi fish.

So, if you want to keep Koi fish in a tank in your home, you need to ensure the tank is big enough to house at least 3 Koi fish. This will make your Koi fish comfortable, which means they will hide less in your tank so that you can get the full calming benefit of the Koi fish.

Use A Muddy Substrate In The Tank

When keeping Koi fish in a tank, you should choose a muddy substrate over any other option. When you think about a Koi fish’s natural environment, they live in lakes and rivers that don’t have a glass or sandy floor.

If you want your Koi fish to be as happy and healthy as possible, you should use a muddy substrate at the bottom of your tank to help the tank match the Koi’s natural environment as close as you can get it.

Koi will dig in the substrate to find food, so keeping a large number of living plants might be difficult, but you can place the plants in areas your Koi don’t seem to dog and use fake plants for the other locations.

Quarantine New Koi Fish For Health Reasons

Before you place any Koi fish into a tank together that have never been together before, you need to quarantine the Koi fish. While the Koi are in quarantine, you must watch them closely for any signs of infection or disease.

Koi fish can become infected by a disease called KHV or Koi herpesvirus, which is fatal to Koi fish and can spread easily among a tank of Koi. This highly infectious disease has a high mortality rate, and it’s not something you want to see your Koi fish go through.

Once a Koi fish is infected, the fish will most likely die within a few days. A Koi fish infected with KHV will have white and red spots on its gills and have difficulty breathing. You should quarantine your new Koi fish for at least two weeks to ensure they are healthy before moving them to your bigger tank with other Koi.

Feed Your Koi Fish A Well-Balanced Diet

Koi fish are big eaters and require a good amount of food to stay healthy. They also need a varied diet that is packed with nutrients. It would be best to feed your Koi fish good-quality, high-protein Koi fish pellets, supplemented with vegetables and fruit four times a week and grain once a week.

It would be best to feed your Koi fish three times daily to ensure they receive the nutrients they need. Regular feeding will also help keep your Koi fish from eating the living plant you place in their tank.

Keep Your Aquarium Tank Covered

Even though Koi fish are large, they are jumpers, and they will try to jump out of the tank your place them in, probably more than once. You need to place a net or tank cover on the tank you keep your Koi in to prevent them from jumping out of the tank and suffocating or injuring themselves.

Koi fish will try to jump out of their tanks more when stressed, so this will happen while they get used to their new tank and new environment, so you need to ensure they are safe.

Keep The Tanks Temperature Constant

Koi fish are freshwater fish used to certain water temperatures due to their native environment. You need to monitor the temperature and ensure it’s 65 to 75°F. If the temperature drops lower than 50°F, this can trigger hibernation in your Koi fish.

If the temperature in the tank reaches above 75°F, your Koi fish could overheat, which could lead to the fish’s demise. With Koi fish, you need to watch the ammonia levels in the water; if these levels spick, this can cause health complications for your Koi fish.

So, it’s important to keep a thermometer in your Koi tank to ensure your Koi fish are kept in the perfect temperatures for them to thrive.

Keep The Tank Clean

When you keep Koi fish in a tank, you need to keep the tank clean. This will require more effort than keeping your Koi in a Koi pond outside, as you will need to clean the tank more frequently to ensure the health of your Koi fish.

You will need to remove the Koi from the tank and place them in a holding tank while cleaning their regular tank. You will need to do this once a week.

You need to replace the water in the tank, clean any algae growth from the tank, and clean the decorations you place in the tank during this once-a-week clean.

How Big Do Koi Get In A Tank? 

As we previously mentioned, the growth of a Koi fish will be self-limited to the size of the tank you keep them in, as with most aquarium fish. However, it is better not to stunt the growth of your Koi fish by placing them in smaller tanks, as this can be cruel and lead to some health complications later.

Suppose your Koi fish does not have the room they need to develop properly. In that case, they could develop issues with digestion and nutrient absorption, and they could have under-developed lungs making it difficult for your fish to breathe correctly.

For this reason, you need to follow the tank sizing chart we provided in this article to ensure your Koi fish can grow to their correct size.

How Long Do Koi Fish Live In Tanks?

White koi fish in a fish tank

Koi fish have long life spans, which does not change when you keep them in a tank inside your home. Koi fish kept in a tank can live between 25 and 35 years. So, when you want to purchase Koi fish, you need to keep this in mind and be certain that you are up for the long task of keeping these fish happy and healthy for their entire lives.


Koi fish can live in a tank in your home, but this does increase their care requirements, and you need to make sure that the tank is big enough to house at least three Koi fish together. You need to ensure that you keep the tank clean and change the water once a week, and you need to monitor the temperature of the water.

If you follow all the information we have gone through in this article, you should have no trouble keeping your Koi fish in a tank. Good luck with your Koi fish!


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