Last Updated on February 14, 2020 by Cooper Fulton

How To Maintain A Thriving Koi Pond (9 Tips)

Koi is one of the hardiest fish and are able to live for many years. Here are my tips that will help you maintain a healthy koi pond, where the koi grow and live longer. maintain koi pond

Believe it or not, koi on average live better in captivity than in the wild. In this article, we will go over the key points in helping maintain your koi pond to flourish and thrive!


Lots of space

Most people’s first reaction when they first build a pond is to get fish. And when they think of pond fish they think of koi.

The thing they don’t think about is the size that koi can reach.

Koi can get pretty massive, on average 15-20 inches, so having more space is key so they can still swim about freely. 

What I’ve found, your pond is best to be 1000 gallons and at least 3ft deep. This will hold up to 5 average-sized koi. To me, I feel this is the perfect size for any pond.

If a pond is too small, it will cause stress on your koi and may become the cause of death

Seeing koi that are forced into contact with rocks, plants, or other fish means you need to reduce the number of koi or expand the size of your pond. 

If you own a large pond I still recommend not exceeding ten koi in any pond. 

With larger amounts of space means koi will grow at a faster rate as well as grow larger in larger bodies of water. 

When selecting the amount of koi you should have in a pond make sure you will have enough room for each koi to have its own space when fully grown.


Good Filtration

Just like in any pond filtration should be the number one priority. Filters are the powerhouse of a pond and if the filter fails, so will the pond. 

A mistake most beginner pond owners make is not regularly cleaning out the filter pads. 

If the filter pads are left without cleaning it can cause low circulation as the pump can get clogged, it can also cause the water not be fully filtered.

If the pond has low circulation, it makes it much easier for algae to grow. It will also allow for the water levels to fluctuate into harmful levels. 

Without maintaining a filtration system it will allow for debris to sink to the bottom of the pond. The debris with start to decompose and release ammonia into the water. 

Without proper filtration maintenance, a pond can lose its circulation and lower water quality. 

Koi don’t need the best of the best water, but keeping up with filter maintenance ensures they will stay healthy. 

A simple way to add circulation is to add pond jets. I have written a guide on all the benefits as well as how to install them.



If a pond has low aeration, it will become a very unhealthy environment for koi.

Aeration is how much oxygen is in the water. If a pond has low aeration it means it contains a high level of carbon dioxide.

Adding oxygen into a pond is very easy a is often overlooked. It can be done by adding in an aerator, fixing the flow of your waterfall, or add in a small water feature.

I love adding water features because they add a nice touch to a pond and also have a positive impact. 

If you are having an algae problem adding some oxygen into the water will help reduce the growth.

An aerator or fountain will help to keep the circulation high in a pond which makes it hard for algae to grow.



Careful Feeding

maintain koi pond

Be sure not to overfeed your koi or any fish for that matter. When you overfeed your fish, the food that is not eaten sinks to the pond floor. 

The food then releases ammonia into the pond which, if you’re not careful enough, can kill your fish. 

A common misunderstanding when it comes to the health of koi fish or any other pond fish is, that the food you give them directly correlates to the fish health. 

Depending on the food you give you it can allow koi to grow faster and larger, more vibrant colors, maintain a healthy immune system, and increase the life span. 

Just like any other animal, if you feed them low-quality food, the health of the animal with also be low quality.

Just like dog food, the price may be higher for higher quality food, but it is well worth it. 

Once I realized the food I was using wasn’t what my fish need, and switched, the results were crazy.

I noticed that the color of my koi increased and stood out in my pond. I also noticed that the quality of my water increased while using the new food.

The low-quality food contained need chemicals that affect the pH and ammonia levels in my pond.

So, you have to be wondering what food I switched to, and that would be the Tetra Pond Koi Vibrance. 

maintain koi pond


Adding plants into a pond has more benefits than just helping it blend it into its surroundings.

Plants can help reduce algae, provide shelter for fish, help filter water, and keep a body of water cool. 

Plants will take nutrients and other chemicals out of the water and use it to grow. This means it filters the water and makes it hard for algae to get nutrients it needs to grow.

Having multiple plants around the pond makes it easy for koi or other fish to have hiding spots if needed. Sometimes fish like to relax and want to find a safe place to do that. 

Having no plants for fish can cause them stress which is never good for fish.

If you have floating plants or plants with large leaves, they will keep the water in a pond cool. 

When a pond starts to get too hot, it makes it extremely easy for algae to take over or to have a large algae bloom.

Plants have multiple benefits and adding them into your pond will help your pond flourish and look great!



Adding places for fish to hide can be the difference between life and death of a fish.

By designing hideouts into the pond you will never have to worry about your fish finding a place to hide. 

Almost all predators to a pond have to look down into the pond to find the fish. 

If a heron is trying to pick a fish from your pond and it has nowhere to hide, it is an easy meal for the heron. 

A simple trick to making hiding spots is to stack several rocks and make small caves around the pond.

If your pond is already built and you have no good hiding spots you can always add in structure. 

The structure is any place a fish can under or in, this can be wood, plants, or even a premade PVC bush.

Using driftwood in a pond makes the pond look natural while still serving a purpose. You can sink a few pieces to the bottom which gives the fish some protection.


Winterize Pond

As the temperature decreases, there are some tasks that need to be taken care of to get your pond ready for winter. Koi are pretty strong creatures and can easily withstand the cold. 

You should add in cold water beneficial bacteria, my favorite is Microbe-Lift Autumn Prep or Aquascape Cold Water Bacteria. 

These contain beneficial bacteria and enzymes, this helps to break down sludge and any remaining leaves in your pond. 

Thus, it sustains biological activity in the cold winter while also maintaining good water quality. 

If you reside in a colder climate where your pond freezes over, for your fish to survive, it is essential to make a hole in the ice. 

This will allow oxygen to enter the pond and carbon dioxide to exit out of the pond. 

Installing a pond de-icer is generally the best choice for keeping a hole in the ice. 

I suggest the aquascape de-icer as this is the one I use for all my ponds.

I’ve written an entire article that goes into further detail on pond winterization if you’re interested.


Water Checks

Doing regular water checks is a must when dealing with koi fish.

Koi produce large amounts of waste every day and can spike in ammonia or other chemicals that can occur very fast. 

By doing regular water checks, at least twice a month, it will ensure your water stays at the highest quality.

One of the highest causes of death in pond fish death from ammonia poisoning. 

Ammonia is something that cannot be by the eye and you won’t know it is a problem till you realize your fish are sick. 

The only way to see if ammonia levels are where they should be is by doing water checks.

Using a water test kit and testing water might be the most underrated maintain a pond owner can do. 

Checking water takes no more than five minutes and can end up saving the lives of your fish.

maintain koi pond


Pond maintenance is something all pond owners must do to keep a pond at the highest quality all year. 

Doing the small in a pond such as removing debris or cleaning filter pads can be annoying and sometimes the last thing anyone wants to do, but it needs to be done

If no leaves were removed in the fall, by the time spring hits, it is likely your pond would become an algae wasteland. 

If the filter pads were never cleaned, who knows what color the water would be.

I recommend going out every other week and just making sure the pond is in tip-top shape. 

Scooping out leaves, trimming off dead plant leaves, checking in on the fish health, and cleaning filter pads. 

By doing this you will ensure that your koi will stay healthy, grow larger, live longer, and have more vibrant colors.


Koi Stocking Guide


Normal Pond Size Surface square feet Gallons at 3’ depth Inches supported 21” koi supported Gallons at 4’ depth Inches supported 21” koi supported
6 x 8 48 1077 107 5 1426 144 7
9 x 9 81 1817 182 8 2423 242 11
9 x 12 108 2423 242 11 3232 323 15
9 x 16 144 3232 323 15 4308 431 20