How Much Space Does a Koi Fish Need? A Little More Than Recommended.

5 min read

Koi fish are big beautiful fish and having a koi pond can be very relaxing for yourself and for family and friends to relax and view the fish

The fact that they are big is the reason that they need a lot of space. The more space they have the better.

Koi fish

The standard size for a koi pond is 1,000 gallons or 6 feet by 8 feet and at least 3 feet deep. Koi fish need one square foot of surface area for every one-and-a-half inch of their body. The proper amount of water helps dilute the large amount of nitrogenous waste that they produce. It is better to give them a little more space than recommended to be on the safe side.

How Big Should Your Koi Fish Pond Be?

There are two main things to remember about koi when you decide how big to make your koi pond or how many koi to put in an already existing koi pond.

The first thing to remember is how big the koi are going to be when they are full grown. You need to leave enough space in your koi pond to account for the size of your koi when they are fully grown.

The reason koi need so much space when they are fully grown leads us to the second thing you need to remember when figuring out how much space your koi need.

The second main thing to remember is that the bigger the fish is the more poop they are going to produce. This may not seem like a big deal to a novice aquarist but if you have any experience with aquariums, you know about the nitrogen cycle.

Because koi are so big, they have massive appetites, so they produce massive amounts of waste. This leads to large amounts of nitrogen and ammonia in the water. You will need a filter in your koi pond but having a large enough water volume coinciding with your koi’s size will help dilute the waste making it less harmful before the filtration.

What Is the Proper Amount of Water Space for Your Koi Fish?

When it comes to water space don’t be stingy. You can figure you need a square foot of water area for every inch and a half of koi.

You don’t need to worry yourself sleepless. Just make sure your koi have more than enough room. There is little margin for error when it comes to keeping your water clean if your koi are overcrowded.

Remember your koi need all of this room because of the waste they produce. They don’t need all of this water space to play, it is for their health.

It’s a consensus that a koi is fully grown after about 3 years. Smaller koi can grow to their full size in 2 years. It is also generally agreed that the average koi fish reaches 8 inches after their first year.

When planning on enough space for your adult koi and you are concerned you won’t have enough space you can just put one less koi than recommended for the size of your pond.

If you do end up with some bigger koi than you planned on having and you are at maximum capacity for the size of your pond, you can get a stronger, larger filter to handle the waste load.

If need be you can always sell or give one of your koi away so that you are at a safe number of fish for the pond size. This can be hard, but it is way better than losing all of your koi fish.

How Much Space in Your Yard or Property Is Your Koi Pond Going to Take?

A koi pond can literally take up your whole yard if you are not careful with your planning.

You can keep koi inside in an aquarium, but you will have to get rid of the when they grow too big for the aquarium. If this happens you can either sell them or give them away.

When you are determining how much space is needed for your koi pond, you also need to figure out how much area you want around it for access. You will also need space for a filter.

The smallest common koi pond size is considered to be 6 by 8 feet and at least 4 feet deep. This makes the koi pond over 1500 gallons so that there is ample swimming space for 10 eight-inch koi and plenty of room for them to grow.

You can also figure this space for a total of 81 inches of koi if you want koi of different sizes.

Koi Fish

When planning a koi pond, make sure the koi have enough space to swim vertically up and down and also horizontally. Koi also need enough room to swim deep enough to escape predators like herons and raccoons.

Your Pond Needs to Have an Access Area

This is just an area along one side of your pond. Access just means that you can walk up to and reach your pond. This area is usually where the filter is so that you can easily service your filter without putting on your diving suit.

It is practical to have an area of around 3 feet around your filter to service it. Service is things like cleaning your filter, replacing parts on it, or preparing it for winter.

People also usually use this area to clean debris from the pond.

It is a good idea to have access all the way around your pond in case your pond starts to leak so you can repair it.

Planning an Access Area Increases the Overall Area Your Pond Will Take Up When Completed

If you add access on each side of a 6 by 8-foot pond it could increase the total space to say 6 by 13 feet. This is why it is important to consider an access area when planning your pond.

You can make as big of a koi pond as you want but the biggest recommended size is 9 by 14 and at least 4 feet deep. This is because sometimes you will have to catch one of your koi and less space will help you catch them faster. This will keep you from stressing out the other koi.

This maximum size will also save you a small fortune when you have to add medication to your entire pond.

How Much Space Do Koi Need for an Indoor Aquarium?

Koi grow fast. They can grow up to 6 inches in a couple of years from being newly hatched. If you start out with small koi, you may only be able to keep them for a year.

Their aquarium needs to be at least 29 gallons.


Having koi might seem daunting but never fear, it is not hard as long as you do things right. Just make sure they have more than enough space to swim around and be able to keep the water clean.

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Pet Aquariums

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