How To Set Up An Indoor Koi Fish Tank (2024)

When setting up an indoor koi fish tank, there are several steps that must be taken in order to ensure that your fish will be healthy and comfortable for the duration of their indoor stay.

Let’s take a look at what you need to do to create a happy, safe space for your koi fish!

To begin setting up your tank, there are a few very basic things you need to understand about koi care.

For starters, koi carp get very large.

In fact, they can even reach lengths of three feet or more when properly cared for!

Due to this, they should not be kept in a tank for their entire lives, as they will not be able to fully grow and thrive in such a confined environment.

Still, when koi are young or are in quarantine, they can be kept in a tank if the conditions are right and the volume is appropriate.

In general, a koi carp needs a tank volume of at least twenty nine gallons if they are young.

Larger koi need fifty gallons a piece; the volume continues to increase as the koi get older and bigger.

Koi fish can live to be more than fifty years old and are smart enough to learn to trust their owners and accept food directly from them.

These intelligent fish are stunning and fun to keep but you have to ensure they have enough room and comfortable conditions if you want to see them grow happily.

When you first set up a tank, it is recommended you let it cycle before introducing any fish.

For some people, this means just giving the filter enough time to move the entirety of the water volume through the filtration media but, in general, most professional koi keepers will recommend giving your tank around two weeks to grow beneficial bacteria and begin a healthy nitrogen cycle.

Once your tank is filter, you need to ensure it is a good temperature for the fish.

This can be done with a submersible heater or under tank heater.

Either way, you should make sure that your water will be evenly heated and that the heater is appropriate for the volume of your tank size.

Indoor koi like temperatures around sixty five to seventy five degrees fahrenheit but can tolerate variances quite well due to their hardy nature.

They also enjoy having light for around eight to twelve hours each day.

The ideal pH reading for a koi enclosure is slightly alkaline.

You should shoot for around 7.5 to 8 but 7 is fine.

Anything lower or higher, though, will be uncomfortable and could even kill your fish so keep an eye on the testing levels of your tank, especially in the beginning or if you notice your fish seeming uncomfortable.

When setting up your indoor koi fish tank, it is important to remember that koi are naturally jumpers.

This means that if you do not have a lid on your tank, you are running the risk of your koi potentially leaping from the tank and stranding themselves, where they will perish if not found soon enough or otherwise injure themselves.

Koi, especially as they get bigger, are fairly active fish so a lid that closes firmly on the tank is a must have for any enclosure.

Additionally, your koi love to sift through gravel and substrate.

They are bottom feeders by nature and adore rooting around for tidbits to eat.

Be sure to add a good, thick layer of rocks or pebbles to the bottom of the tank for them to dig through.

Around two inches or so should suffice, though they will not be opposed to a bit more.

Hides and other objects are great too, since the koi like shade, but be warned that they may move things about.

Koi do not do well with drafts.

Try keeping them somewhere that has steady airflow and remains stable in temperature.

Additionally, try to keep them out of direct light since bright sun or light exposure can result in algae overgrowth which can throw off the nitrogen cycling of your tank, especially if you are struggling to keep up with the rigors of cleaning up after messy koi fish.

Koi fish need a lot of space.

You have probably heard this a dozen times or more but they really, truly need to be in a koi pond once they begin to grow large.

They are active and produce a lot of ammonia and other waste products so leaving them in a tank for their entire lives is a death sentence.

This is also true for overcrowding.

While it may look pretty to have a lot of koi in your tank and be very fun to watch, koi fish should not be overcrowded, as it can cause significant health risks including injuries due to fighting and lack of space.

Illnesses and diseases can rapidly spread through an overpopulated tank, resulting in potential mass death or mass epidemics.

Koi are hardy fish but when stressed their immune response drops, making them more susceptible to illnesses and parasites.

Overcrowding is, of course, stressful for your fish, so this scenario creates a perfect storm for bad things to happen within your tank.

If you notice any ill or injured koi, be sure to immediately remove them from their main tank and place them in a suitable quarantine tank.

Koi can heal up quickly but they should still be quarantined for at least a month to ensure they are not bringing any germs back to the rest of the population.

While good for young koi, tank enclosures are a temporary setup that offers a nice, dynamic display as you adjust to keeping koi.

It also works amazingly as a quarantine area and offers you a little more control over your population in the event of illness, injury, or other issues.

Set up a large enough tank with stimulating rocks and hides and your koi should be just fine until their new pond home is ready!