Can Koi be Kept in a Fish Tank/Aquarium

Yes, the playful ornamental Koi fish can survive in a tank/aquarium, its growth and health are dependent on its environment. Let’s look at the factors to be taken into consideration while setting up the koi in the fish tank.


Koi grow fast and big. An average adult Koi can grow anywhere between 24 to 36 inches in length in the span of 1-3 years. This factor decides the size of your tank and the amount of water too.

Koi in the Fish Tank / Aquarium

If you don’t already have one, a new tank is required and its size can be determined based on the number of Koi you intend to keep & by measuring the amount of water required for each fish the size of the tank can be determined according to your preferences.



Aquarium Stand

As Koi tanks can be big and filled with gallons of water, it takes a durable stand to withstand the aquarium’s weight.


Koi are active and docile creatures and can have a tendency to jump, which might result in the fish accidentally jumping out of the aquarium along with the water spillage which can be caused by the casual jumping/flapping of Koi, can be avoided by using a canopy which acts as both protection to the fish and a cover to stop any excessive spilling of water.


A general rule of measure for water is 10 gallons per inch of the Koi, for example, a 16-inch Koi in the fish tank would require 160 gallons of water.

Water Temperature

Koi can survive in water temperatures ranging from 35*F- 90*F, while the optimum temperature for the koi in the fish tank is between 65*F-75*F (18*-24* Celcius). Make sure the water isn’t too cold or hot, the water temperature affects their eating habits.

A heater can be used to regulate water temperature, if you want to maintain a bit cooler temperature set it to around the room temperature and notice the activity of the fish, if they seem too lazy/lethargic slowly turn off the temperature and set it at a point where the fish seem active enough as cooler temperatures make them more dormant.


Although heaters might have a built-in thermostat they are known to fail at times, so maintain a thermometer to gauge the aquarium’s water temperature.

Filtration System

Active Koi can eat a lot and produce a lot of waste, a filtration system helps in cycling the water and keeping the aquarium clean. A Koi tank needs a filter that can cycle the whole water 3 to 5 times every hour to keep it clean.

Also, Koi like moving water produced by the filter, it keeps them active. This also reduces the frequency of water change. Contact any retailer/manufacturer to get the right filter according to the size of your tank.


Koi prefer highly oxygenated water, an aeration system can keep help with the necessary dissolved oxygen and produces bubbles for the fish to play with. Higher water to air-surface space works as a natural oxygen supplicant compared to tanks which have less space at the top.

Live Plants & Substrate

Adding live plants and a substrate to the bottom of the tank can enhance the habitat and give a more lively and natural feel to the environment of the fish.

  • Live plants can bring a natural feel & floating live plants may also be added to the aquarium, though too many of them might block the natural light. Make note that though all fish do not, a few of them might eat the plants depending on the fish.
  • A muddy or woody substrate can be used to improve the feel of the habitat.
  • Also, fake removable plants can be added to avoid any mess.


On the ornamental side, lighting would make the tank attractive and keep the fish active. The lights can be lit for anywhere between 8 to 12 hours and give the fish an environment of complete darkness for 8-12 hours.

Cleaning Kit

Maintain essential items required for cleaning & maintaining a healthy environment of the tank including net, filters, and algae scrapers.

Companions for Koi in the Fish Tank

Koi themselves grow big and occupy space so consider it before getting other companions. They are usually peaceful and playful fish and can coexist with other fish, they might pick on other slower fish. Usually recommended companions are

  •  Goldfish
  • Chinese Hi Fin
  • Golden Ofre
  • Catfish
  • Tench

Indoor Environment

An indoor environment is good for the aquarium/tank to avoid direct sunlight as it can affect the water temperature. Also, make sure to keep the tank away from any other animals which might bully the fish.

  • Unless you have space large enough as a pond, the indoor environment can be limited in terms of space as Koi can get large quickly(a couple of years) and tend to live longer, so the initial size of the fish needs to be taken into consideration before moving koi in fish tank.
  • Keep the environment of the aquarium/tank clean as it affects the health of the fish, and notice any unusual factors which might indicate any disease

So the final tank size and number of Koi is based on the space available and personal preference considering the above-mentioned factors along with the important one the initially desired fish size which influences other factors.