The Basics of Koi Fish Tanks

The Basics of Koi Fish Tanks

When keeping koi fish, sometimes it is not reasonable to plan out an entire pond due to space, money, or time constraints.

Ponds take a massive amount of work and can be tricky.

Due to this, some people prefer tanks.

While hotly debated, there are some things you can do to ensure your koi are happy and healthy in their indoor home.

Here are some tips and tricks for raising healthy, happy koi right inside your own home in your well-equipped koi fish tank.

Minimum Requirements

The most important thing to remember when keeping koi indoors is that they require a lot of space.

Each koi fish in a given area needs around fifty gallons of water and a depth of at least three feet.

If you have more than one koi, you need more water per fish.

As they grow, this amount may increase, as well.

Needless to say, you will need a massive tank if you plan to keep koi long term.

This can cost pretty much the same amount as a koi pond and requires roughly the same amount of work.

If you were looking to avoid this aspect of koi keeping, a pond might be the better choice in the long run.

Still, if you specifically want to keep your koi in a tank, please keep these requirements in mind and remember that more space is always better.

Your koi are big, beautiful fish so be sure to give them the life, space, and respect that they deserve!

Your koi will also need adequate filtration and aeration for their tanks.

This means you must buy a filter that can handle the volume of water that is contained within your tank of choice.

Not every filter can accommodate larger volumes so do your research and make sure the one you choose is suitable for your large koi.

Koi are also naturally bottom feeders and prefer to be able to root around in their environment for scraps.

Due to this, you need to include at least three to four inches of substrate in the tank for them to move about in.

This can be done as gravel or small river rocks, just be sure the medium is free of any toxic materials and safe for aquatic use.

The Basics of Koi Fish Tanks

The Problem with Long Term Indoor Husbandry

While koi may be sold small, it is worth considering keeping your koi outside once they begin to get large in size.

Koi simply are not happy unless you can have a massive tank setup for them.

If you are offering a fifty or one hundred gallons, they will still eventually want a little more space, especially if you are keeping several.

Other issues often arise with keeping koi indoors, as well, though.

Koi are more likely to be stressed which opens them up to illnesses due to the fact that stress impacts the immune response of fish.

Additionally, since your koi are in such a confined space, illnesses will spread much more quickly.

This can cause a mass illness or even mass death event within your koi collection.

Some people have reported having their entire tank wiped out.

Your koi will also be exposed to higher waste levels since the natural water cycle will be much different than an outdoor setup.

Due to this, ammonia levels can build up and pose health risks including low oxygen levels if you are not properly keeping up with maintenance, especially if your fish are beginning to size out of their enclosure. 

Due to this, it is really recommended that you keep your koi outside if at all possible or consider keeping smaller fish if you have no plans of sizing them out of their tank once they are of a larger size category.

Quarantine and Temporary Tanks

Even with temporary setups, koi need their minimum requirements met.

They are large fish and, even if just for a few days, they need plenty of room to move.

Just a few hours in a smaller enclosure can cause stress or injury.

Some people have even experienced their koi jumping out of tanks that felt too small due to the stress and fear they experienced.

Using temporary tanks is a good way to keep diseases or other issues from spreading upon the introduction of a new fish into your pond.

It is actually recommended to keep your koi in quarantine for several weeks to prevent exposing your entire colony to any bacteria or other issues your new addition may be carrying.

To set up a quarantine tank, you do not have to go all out and add a ton of hides and decor pieces.

These can be minimalistic setups that allow you good monitoring abilities so you can catch any issues early on.

Additionally, these temporary tanks are helpful if your koi are ill, as you can quickly single them out and remove them from the pond before illness begins to spread.

Catching aquatic bacterial, viral, or parasitic illnesses early is key in preventing an epidemic from forming in your pond and can make a massive difference in the amount of work and money that will have to go into getting your fish back to a generally healthy state.

Due to this, many people keep a spare tank already cycled or otherwise maintained or have the parts available to quickly prepare a quarantine tank if needed.

Having a good plan will minimize the exposure your fish experience to any issues and prevent any injured fish from becoming worse off due to exposure to the rest of the group while healing.

The Basics of Koi Fish Tanks

To Tank or Not to Tank

This is a question that is very, very controversial within the fish keeping community.

Generally, it is recommended to keep koi outdoors in a pond if possible but smaller fish usually do well within a large tank setup until they age and grow too large.

Either way, having a tank ready to go is a good idea since injuries and illnesses do sometimes happen.

Having a tank can keep issues minimized and ensure your koi are happy and healthy all year round.