Can You Keep Koi In A Fish Tank? (Tips and Size Guide) - Fish Tank Master (2024)

Koi fish have long been used to add a touch of elegance to one’s home. These huge fishes can grow up to enormous sizes, so you may have only ever seen them in a pond outside – at least, that is the ethnic, Japanese image.

However, many people are unaware that these large goldfish can actually be kept at home as well!

You most certainly can keep koi in a fish tank at home, as though they can increase a great deal in their size, it is only limited to the size of their surroundings. So if you were to keep koi at home, they will adjust to your tank’s size, though a large one is still recommended.

These fishes are fancy, and there are other factors as well, that need to be met when keeping koi as pets. If you would like to know more, continue reading this article!

Can You Keep Koi In A Tank?

Though you will normally find koi fish in backyard ponds, it is possible to keep them in a tank. In fact, they can add a beautiful touch to your living room and may even thrive well indoors in harsh conditions.

These species of fish grow up according to the kind of container they are in, so if kept in an aquarium, they will grow to fit in it.

However, being big fish, you have to be careful and keep a closed tank, as koi like to jump and try to make an escape. The ideal temperature for the survival of koi fish is around 41-91°F, so they survive in most kinds of places.

They are also very hardy and can live to go without food for at least a week.

Koi may also benefit from being kept in a tank. During winters, when the water gets cold, koi may not survive outside, but if kept in an aquarium, they remain active in the steady temperature of the water.

They may even live a happier life with the water being adjustable according to the weather.

These fish are also known to be quite friendly, and they can also make for very active pets for fish, considering it is possible to teach koi some tricks, like how to feed off your hand.

More:How Much Are Koi Fish?

What Is The Best Possible Setup For A Koi Tank?

It is possible to keep koi at home, but being fancy fish, they require some altered certain conditions for their survival. In order to keep koi, the following are the most important things you need to keep in check.

1. Setting Of The Tank

The most basic requirements for the survival of your koi in a tank are its pH levels, the perfect temperature, and a proper filter for cleansing. These fishes can survive at a pH level of 7.2 to 7.4 (alkaline), but not lower than that, as they might suffer from Acidosis.

Make sure that you let your tank filter complete one cycle during the setup.

Letting your tank go through nitrogen filtration once will allow the healthy bacteria to grow, which is good for your koi. You also need to keep the aquarium at a temperature of 18-31°C as they need warmer conditions to thrive.

An underwater heater is better as it can transmit heat evenly throughout the tank.

You can also install a light for your aquarium as these fish require around 10-12 hours of light every day. Make sure that these conditions are met at all times. Keep an eye on your fish as well, as anytime you notice discomfort, you might want to adjust the settings for them.

2. Interesting Environment

Tanks have many modern, adjustable benefits, but being creatures of the wild, compared to a pond, koi would most likely feel bored in a tank.

As mentioned earlier, they also like to try to escape from their aquariums, which happens due to boredom, and sometimes out of uncomfortable water conditions.

Koi are very energetic fish by nature, so to avoid any accidents, make sure that you get a tank with a lid for avoiding any accidents.

However, to fix the direct root of the problem, you have to make sure that there is enough stimulation for your pet in its surroundings or aquarium accessories.

These fishes really enjoy playing with aquarium pebbles and substrate. They enjoy sorting rocks and looking for leftover food between the gaps, so having the substrate full of aquarium plants, pebbles and grains will give them enough to do. Just around 2 inches of rocks would do, as more would be space-consuming.

You can also add other sculptures, corals, and other decorations that add to the aesthetic scene of the aquarium. A shady sculpture would also be a nice addition as koi like to hide and sometimes move around these tiny objects as well.

3. Maintain Natural Surroundings

Being natural creatures of the outdoors, it is important that your koi get enough sunlight and oxygen as much as the living conditions they require.

Keep your tank in a space in your house that gets enough sunlight and air. Keeping a tank in the cold and shade can contribute to the growth of algae in the tank from the dampness.

Algae can stop the nitrogen cycle, which is required for the survival of koi. Make sure that your tank has enough space for the free flow of air so that it is easier for you to clean as well.

4. Enough Space For Each Koi

Koi are big fish, and they require a lot of space to grow, so it is not ideal to pile all of them together like one normally does with other species.

Though they adjust to the size of their container, sometimes, koi fish can grow bigger than their tank. A crowded fish tank would mean a lot of ammonia and waste from the pets.

This might make them feel uncomfortable in their living surroundings, and even cause them irritation. Additionally, lack of space can also force them to fight for room in a small tank.

For around 6 koi fish of about 4-6 inches, a tank-sized 15–20 gal shall be enough to stop overcrowding.

As a responsible fish owner, if you are buying koi, remember to upgrade if the size of your pet increases – or else, you might be facing a number of mass deaths.

If you have a sick fish, keep them quarantined away from the others as these fish are really fragile by nature.

More:How Long Do Koi Fish Live?

How Many Koi Fish To Keep In A Tank?

Since ponds are the ideal habitat for koi, it can be tricky to understand how many koi to keep in a tank. Being a robust species, koi have a long lifespan, can live up to 24-34 years, and even grow up to 22 to 26 inches long. Following is a table to help you get an idea of how many fish can fit in a tank.

Size Of FishSize Of Fish TankNumber Of Fish To Keep
4 – 6 inches15-20 gallons6
4 – 6 inches40 gallons15
6 – 8 inches15-20 gallons3
6 – 8 inches40 gallons7

This is also the standard rule-of-thumb that you can follow in order to calculate how many fish you can keep depending on the aquarium size you choose.

How Do You Keep Koi In A Fish Tank?

Keeping koi in a fish tank can be a difficult task, and they are definitely not the species for first-time fish owners to start with. Hence, the following are a few tips you can use as a beginner koi keeper.

1. Setting Up A Location

No matter what size your aquarium is, make sure that you keep it on a smooth surface that gets enough sunlight every day so that the growth of algae can be avoided. Make sure it is not direct sunlight, as that can alter the water’s pH and temperature levels.

Also, keep it in a quiet place as noise can disrupt the mental peace of the koi and cause them a lot of stress. You can also keep it near a place with easy water access as aquariums require frequent water changes.

2. Filling Up The Tank

Clean the tank thoroughly before you fill it with water. Do not add tap water, as it can be too hard for any fish to live in. If you are using normal water, make sure to filter it out, or let the aquarium filter do the job of cleansing.

Always check the pH level and temperature of the water before you put your fish in. This is a very important step as all requirements must be met in order to help your pet koi survive.

3. Putting In The Koi

Before you put in the koi, you should try to get them used to the water’s temperature. This can be done by first putting your fish in plastic bags and then letting them float over the water for around half an hour. Remember that the ideal temperature for koi to survive is 67–77° F.

4. Aftercare Of Tank

Maintaining the tank is also extremely important. As responsible fish owners, clean your aquarium once at least 2 weeks. This can be done without taking your fish out as well.

Simply prepare the refill in a bucket using a de-chlorinator and clean your filter by rinsing it lightly.

This method shall be followed for a quick clean, but at least once a month, do a thorough cleaning of your tank. You can also add other additional bacteria to ensure it is enough for your koi to survive.

How Long Do Koi Fish Live In A Tank?

Although koi grow up to be very large and can fight for dominance in a small container, they have extremely long lifespans for a fish species.

Generally, domestic koi (western variants) have a lifespan of about 15 years and Japanese koi have been known to have an average life span of about 40 years.

Hence, koi in a fish tank with proper care and maintenance have a chance of surviving even up to 24-35 years or even more. So, if you are planning to get koi, know that you are investing in a long-term commitment.

What Size Tank Does A Koi Fish Need?

On average, there cannot be a tank too large for koi. Fish, in general, like to have a lot of space to swim around as their natural habitat is in the option.

Even if you were to get a tank-sized 1500 gallons, it would be great for your koi. In fact, if the tank is not large, you might even have difficulty with your growing koi.

If you start out with baby koi in a small tank, you might have to increase the size of the aquarium anyway as your pet grows. Hence, getting the larger size from the very beginning is not a bad idea, except if you detest cleaning and maintenance.

What Fish Can Live With Koi In A Tank?

All fish that require the same conditions as koi can be put into a tank with them. Ideally, medium-sized fish would be preferred, as koi can grow to be quite big, and smaller fish can get eaten by them, causing problems.

You must also make sure that you get your other fish from a reliable source so that they do not bring in disease.

A lot of fish can grow to live with koi – grass carp, goldfish, redear sunfish, suckermouth catfish, Chinese high-fin banded shark, largemouth bass, and orfe are some species to name a few.

How To Take Care Of Koi Fish In A Tank?

Apart from giving your koi all the basic necessities and living requirements, there are some other things you can benefit from knowing. The following are a few tips on how to take care of koi in a fish tank.

Have Enough Room For All Your Koi

Having enough space for every koi is the most important thing to remember, as size is a very common problem faced by koi owners.

Remember that the compactness of space can stunt the growth, and in some cases, cause accidents because irritable koi like to jump out of the water.

Maintain Clean Water

Not only do you need to maintain your aquarium’s hygiene every few weeks, you can also add extra minerals by adding granulated carbon or an under-gravel filter.

As a rule of thumb, the filter should process 350 gal. of water for every 12 inches of fish. Also, avoid overfeeding to avoid the production of extra waste.

Since koi go around the substrate a lot, clean the gravel at least once every week. Lastly, make sure that the pH, ammonia, and temperature of your tank are always balanced.

Aquarium Change During Winter

During winter, temperatures can drop quite a bit in the aquarium. If you notice a change in your koi’s behavior, you can shift your koi into an open tub of around 300 gallons temporarily.

Related Questions

What Is The Minimum Tank Size For Koi Fish?

Since koi are big fish, the minimum tank size approved for the healthy growth of your fish is at least 240 gallons.

How Big Of A Tank Do Koi Fish Need?

Koi fish need a tank size of at least 240 gallons to grow healthily and have enough space to swim around.

Can You Keep Koi In A Fish Tank? (Tips and Size Guide) - Fish Tank Master (2024)


Can You Keep Koi In A Fish Tank? (Tips and Size Guide) - Fish Tank Master? ›

If you want a permanent indoor setup, space is critical. The bigger the better for koi—and remember they need large water filters. Be sure your indoor pond or aquarium has room for a fully grown adult koi to turn easily and not run into each other or the walls. You will also need to maintain a robust filtration system.

Can you keep a koi in an aquarium? ›

If you want a permanent indoor setup, space is critical. The bigger the better for koi—and remember they need large water filters. Be sure your indoor pond or aquarium has room for a fully grown adult koi to turn easily and not run into each other or the walls. You will also need to maintain a robust filtration system.

What size tank should koi be in? ›

Koi grow quickly and get very large. Keep mature koi in an outdoor koi pond of at least 3 feet deep, with at least 240 gallons (908 liters) of water per fish.

Will koi stop growing in a small tank? ›

The size of a pond will not stop a Koi from growing. The size of the pond, along with other factors like health, feeding, water temperature and water quality affect the speed of their growth. A Koi will keep growing until it has reached its genetically predetermined size.

Is 1000 gallons enough for koi? ›

Second, due to pheromones and toxin control, we want to stay at or under four koi per 1,000 gallons of water to promote a healthy living environment. These recommendations are a starting point and would be the all-encompassing answer to the question if it were a simple question.

How long can koi live in an aquarium? ›

The answer to 'how long do koi fish live' differs between Japanese and domestic versions. Domestic koi fish tend to live for about 15 years on average. This is much less than Japanese koi. Japanese koi fish have a longer average lifespan of 40 years. Some can even live well into their 60s!

How long can I keep koi in holding tank? ›

Please cover the quarantine container right away as your koi will jump out. Please remember keeping koi in a separate quarantine tank to up to 21 days it the best way to ensure health going into your already established pond system.

Do koi grow according to tank size? ›

Koi are easy to keep, and an aquarium takes up little space. Koi adapt to their environment and grow according to their space. So they will not outgrow the aquarium nor jump out.

How many gallons does a koi need? ›

If you've got a well-set up, stable pond, a good rule of thumb is 1” of fish for every 10 gallons of water. So for an immaculate 500 gallon pond, you can safely accommodate no more than 50” of fish. That sounds like a lot, but accounting for an approximate mature koi size of 12”, that allows only 4 fish.

Can small koi live in 10 gallon tank? ›

Don't waste your money or the koi's life by putting it in a tiny tank where it will die. They need lots of room. None. A 10-gallon tank is much too small for koi.

Do koi fish jump out of tanks? ›

However many are not very common and lot of them are preventable. Why do koi jump out of water? This jumping behavior is most often seen by koi that are new to their environment. Koi are fairly smart fish, and as such they like to know their surroundings.

Can I keep a koi fish in a 5 gallon tank? ›

For each koi you have, we recommend 250 gallons at MINIMUM!

Congratulations! You've likely stunted your fish.

Do koi jump out of aquarium? ›

Koi Jumping Can Be Both Interesting and Deadly

If you've ever been in the presence of a pond full of koi fish for an extended period of time, you may have noticed that under certain circ*mstances, these acrobatic fish can (and will) actually jump out of their habitat.

How many koi can go in a 40 gallon tank? ›

A Koi Fish minimum tank size probably shouldn't be less than 50 gallons for as little as two or three fish.

Can you have just one koi fish? ›

Koi carp are social fish and are often kept in groups in outdoor ponds or aquariums. While a single koi can survive on its own, it may not thrive or display its natural behaviors without the company of other koi. Keeping a single koi carp alone for an extended period can lead to boredom and loneliness.

What is the minimum size for a koi pond? ›

Backyard koi pond sizes can range from 6 feet by 8 feet to 20 feet by 30 feet and larger. The size of the average pond can change from area to area but it's usually about 150 square feet. Ponds smaller than 6 by 8 feet aren't good homes for koi fish. Smaller backyard koi ponds are at least 6 feet by 8 feet.

Can koi fish live in aquarium without oxygen? ›

Fish require oxygen to live. Therefore whatever tank pond or lake they're in must have moving water. If the Koi are in a lake or stream with moving water they'll be fine. If they're in a pond, a fountain should be installed to keep the water surface agitated.

Can koi fish survive in freshwater? ›

Koi and goldfish are the most popular freshwater, ornamental fish throughout the world.

Can a koi fish live in a 10 gallon tank? ›

There are a few different calculations that you can use to estimate the most appropriate koi fish aquarium size. The generally accepted rule of thumb is that you'll need approximately 10 gallons of water for every inch of fish. Another calculation that you can use is providing one cubic foot for each inch of fish.

Does koi fish need oxygen in aquarium? ›

Koi require 6mg/l of oxygen in the water for good growth and health. To achieve this you need to make sure you have a good pump running into your biological filter as well as having a Venturi or air pump with multiple air stones leading into different areas of the pond.

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