How to Build a Koi Pond in Your Backyard

Adding in a koi pond will immediately add a sense of peace and relaxation to your backyard. Building your own can be a fun project, and you’ll feel a sense of accomplishment each time you’re outside watching your fish. Learning how to build a koi pond in your backyard can take some time, but it is completely worth it. In this article, we cover exactly how to build your very own pond as well as maintaining it so that you can enjoy it for years to come!

What You’ll Need To Get Started

While you can customize your koi pond to create what you want, there are a few materials that are required, no matter what. Below is a list of the things you need to get started.

  • Liner: You’ll want to use an EPDM liner (45 mils) to line the pond as well as behind any waterfalls, streams, or other water sources. This fabric is durable but flexible.
  • Skimmer and Skimmer Pump: Much like a pool skimmer, the skimmer for your koi pond will pump water through a basket to collect unwanted debris.
  • Pressurized Filter with UV: Having a pressurized filter is going to help you keep your koi pond nice and clean.
  • Solids Handling Pump: The solids handling pump can handle both small debris and sludge. You can place this at the bottom of your pond.
  • Aerator: You’ll need an aerator to oxygenate your koi pond. Oxygen levels can change depending on the temperature and time of day. You’ll need your aerator to add supplementation during the times that oxygen levels are low.
  • Ionizer: As the name suggests, an ionizer will release ions into your pond. This is the only mechanism that controls and even eliminates string algae.
  • Float Valve/Electronic Water Level Controller: One of these will typically be added to the skimmer, and will be used to keep a constant water level.
  • Pond De-Icer: If you live in an area where you experience freezing temperatures, you’ll use a de-icer to prevent ice build-up and keep your fish alive during the winter.
  • Lighting: You can add light to the inside or outside of your koi pond as you please. You’ll want enough so that you can enjoy viewing your pond at night.
  • Fish: What is a koi pond without fish? You can add either pond fish, such as goldfish, koi fish, or a combination of both to your pond.
  • Plants: Adding plants can change the atmosphere and look of your koi pond, but that’s not the only purpose it serves. It’ll also provide natural oxygen as well as a source of shade for your fish.

To keep things simple, we are going to give you the tools to create a koi pond without a waterfall. If you would like to add a waterfall to your koi pond, you’ll need a few more things.

Below are optional items you’ll need only if you plan on having a waterfall:

  • Underlay: The underlay is a thick filter cloth material that is used underneath to provide additional protection.
  • PVC Flex Pipe, Fittings, Glue, and Primer: You’ll use PVC flex pipe to connect pumps to filtration and then to the spillway. PVC flex pipe is durable and flexible. The PVC fittings are used for durability to keep pipes from overheating or freezing. The glue and primer will be used to fuse the pipes to the fittings.
  • Up-Flow Filter or Spillway: A spillway or an up-flow filter is used to diffuse water and create an even flow in waterfalls.

Step One: Evaluate Your Space

Choosing Where to Place Your Pond

Finding the perfect spot for your koi pond is vital. You’ll want to avoid any areas that have large trees with root systems that get in the way. Of course, you also want to steer clear of any electrical lines.

Areas with partial sun tend to be best for koi ponds containing fish and plants. Where you place your pond will dictate the types of plants you can get. Full shade areas will limit plant selection, while full sun areas run the risk of the water getting too hot.

Many people like to have their koi ponds close to the house. If you’re able to, having your koi pond nearby allows you to watch whether you’re in your backyard or in your home looking through the window.

Determine How Big You Want Your Koi Pond

A big beginner mistake to avoid is making your koi pond too small. Before committing, roughly trace out where you’ll place the pond and how big you’ll want it to be. Remember, you want there to be plenty of space for all the equipment necessary, water for fish to freely swim, and plants to bring it to life!

Although it may seem huge, it is recommended to make your koi pond at least 1,000 gallons and three feet deep. If you plan on having a decent amount of fish, you may want to make it even bigger. A six-foot by eight-foot pond that is three feet deep yields exactly 1077 gallons, which is a good place to start.

Step Two: Start Digging 

Before you start digging up dirt, make sure you have everything marked precisely how you want it. Measure the length and width you’d like your pond to be and use marking paint to draw out the exact placement. You’ll also want to draw out other components of the pond such as the skimmer, falls, and filtration.

Clear Space

Creating a clear workspace is going to make your job a whole lot easier in the long run. Between the large pieces of equipment and moving around the pond, you’ll need a bit of extra space to work in.

Start removing any vegetation nearby where you’ll be placing your pond. Clean up any grass trimmings or leaf piles that could blow into your workspace. 

Put away any furniture, toys, etc. that may be lying around in the backyard. Once the pond is finished, you can put everything back as it was.

Dig Your Pond

Grab a shovel and get to work! If you can get a significant other or friend to help with your project, this will help to speed up the process. The top of the pond will be the widest, so as you dig, start at the perimeter and slope down as you reach the center if possible.

As you dig, use your creativity to create a uniquely shaped pond. Adding shelving can give your pond some extra character!

Step Three: Place Equipment And Liner

Laying out all of the equipment beforehand will help to simplify the process later on. Place and backfill the skimmer and the spillway. Get a general idea of where the flex pipe will go (if using), typically behind any falls.

Add Liner

You’ll want a sturdy underlay material such as a 45 mil EPDM Liner. The liner should be a little bigger than your pond, at least one foot extra around the perimeter, so you can adequately secure it in place.

Before placing the liner, look around and make sure there aren’t any sharp rocks to prevent the liner from getting damaged. 

Grab a couple of friends to help you roll out the liner over the hole, carefully placing the liner over the dirt. Leave at least one foot of liner past the perimeter so that you can easily secure it.

Step Four: Add Rocks

Purchase rocks of all shapes and sizes. You’ll want some large stones along with smaller pieces of pond gravel. When searching for rocks, be sure that they are specifically made for ponds. Any rocks with sharp edges could end up damaging the liner.

Start With Large Rocks

Start by placing your larger rocks or stones on the liner around the edge of your pond. Think creatively when arranging your stones to make it look exactly how you want.

Once you have all of the large stones laid out how you like, start filling in the smaller spaces with the rest of the rocks. Adding the pond gravel to the bottom floor and shelving will help to create a more nature-like atmosphere. 

To prevent rainwater from getting into your pond, keep one foot of the liner exposed behind the rocks. If you plan on adding a waterfall, add waterfall foam between the rocks to prevent water from slipping through.

For the best water quality, flush out the stones with water and pump out the dirty water.

Dig a High Ridge

To further keep rainwater, grass clippings, and other debris from reaching your pond, dig a 3-inch high ridge around the entire perimeter. Use a spade to shift the dirt into a ridge formation up against the rocks. 

Add Lighting

Once the rocks are arranged how you like, you can start looking for spots for underwater lighting. When placing, position the lights away from the main viewing area.

Step Five: Fill With Water

You can watch your koi pond come to life as you begin filling it with water!

Use a hose to fill up your pond. If needed, remove chlorine by adding a de-chlorinator, a carbon charcoal filter, or a water conditioner. Remember, chlorinated water can be toxic for fish, including koi. If you do need to treat chlorinated water, be sure to do this before adding fish to the water.

Once fish are in the pond, treat the water outside of the pond before adding it in. When changing the water in the future, do it in smaller amounts at a time to prevent fish from going into shock.

Adjust the Water

The pH level of your water should be 7 and 8.6. To check, use a water testing kit to ensure that the pH and dissolved nutrients are at the correct levels for your fish. Continue to adjust the parameters of the water as necessary.

Ensure that the temperature of your koi pond is around 65 degrees Fahrenheit before adding fish. Although koi fish can survive in water that is anywhere from 34-90 degrees Fahrenheit, they will thrive when it is near 65 degrees.

Regularly check the temperature throughout the day. An aerator will help regulate temperatures, but in colder months, a pond heater can be helpful as well. If the water is becoming too warm, gradually add cool water throughout the day.

Step Six: Install Equipment

Install a Filtration System

Go to a pond equipment supplier to find a filtration system, and follow the directions they give carefully. Using a filtration system will keep the pond water clean and high quality to keep your koi fish healthy.

  • The settling chamber allows you to easily remove debris from your pond so you can keep it clean.
  • The mechanical filtration seamlessly catches debris while floating through the pond water.
  • Biological filtration will reduce ammonia and nitrate levels, both of which can be toxic to your fish, such as koi.

Place the Aerator

As mentioned before, the aerator will keep the pond water continuously moving. This oxygenates your pond promotes gas exchange and prevents the water from freezing as the weather gets colder.

Before purchasing your aerator, make sure you know the volume, shape, and depth of the pond to ensure you’re getting one that’s the correct size.

If you have a pond aerator, you likely will not need a pond heater.

Turn on both pieces of equipment before adding fish.

Step Seven: Add Plants

Choosing Your Plants

Adding plants to your pond will provide oxygen for the water and shade for the fish. Try to find a variety of surface, emergent, and submerged plants for your pond.

During hot months, having a good amount of plants can help keep the temperature down in the pond. If you have a large, deep pond, you may not need as many plants.

Here are some of the different types of plants to choose from for your pond:

  • Submerged Plants: As the name suggests, submerged plants are plans that are entirely below the surface of the water. Some examples of these are coontail, eelgrass, and pondweed. It is important to keep the roots safe by covering the bottom of your pond with rocks. This will keep the fish from digging them up when looking for food. Once planted, these plants require little care. 
  • Surface Plants: Surface plants will float on the surface of your pond without needing their roots covered in dirt. These are great plants for providing shade for your fish to keep them cool in warm months. Some examples of this plant are fairy fern, water shield, and water clover. 
  • Emergent Plants: This type of plant is rooted in the ground, yet the leaves and flowers will still be visible above the surface. Some examples of emergent plants are cattails, flowering rush, and yellow lotus.

When to Add Plants

It isn’t necessary to add your plants in before adding your fish; however, you should add them all at once. If you only add a couple of plants, the fish may get a little too curious and destroy them. By adding lots of vegetation at once, it keeps them from giving all of their attention on only one plant. 

To learn what the best plants for water gardens are, read this article.

Step Eight: Add Fish

Once your pond is all set up and ready to go, it is time to add in the fish.

Keep your fish in the plastic bag and water you purchased them in. Let the bag float on the top of your pond for a half-hour so they can gently adjust to the temperature.

Then, add some pond water to the bag, retie it, and let it float in the water for another 30 minutes to help them adjust. If it is a hot day and there is no shade, you may want to place a towel over the bag to keep them from getting too hot. 

Once your fish have adjusted to the pond water, you can open the bag to release them into their new home. 

Best Fish For Your Koi Pond

Although it is called a koi pond, this doesn’t mean you’re just limited to koi. There are a lot of fish varieties that can thrive your pond, and even live 30-40 years in it!

Here are some of the best fish for a koi pond:

  • Koi Fish: With over 100 types of koi fish to choose from, you won’t be limited in your selection. Koi fish are pretty smart, and you can even train them to eat out of your hand! This makes them a great pond fish if you’re looking to have a little more interaction with your new pets. 
  • Grass Carp: Grass carp is a large herbivorous fish that loves to feed on algae. Now, you may not want to purchase too many of these as they can sometimes eat so aggressively that they overdo it. This can quickly go from algae control to disrupting your pond’s ecosystem. 
  • Goldfish: Goldfish are a popular type of fish for a koi pond for many reasons. They’re cheaper than other varieties, stay healthy, and are gorgeous fish to watch swim around! If you have a larger pond, you may get to watch your goldfish grow to over a foot long! The only potential negative of having goldfish is how rapidly they reproduce, so you’ll have to stay on top of population control.
  • Sunfish: Also known as pumpkinseed fish, sunfish are a great fish to have for insect control. These fish feed on mostly insects and parasites, but can sometimes feed on other fish eggs. Like goldfish, they reproduce rapidly, so you may not want to purchase too many of these. 

Step Nine: Koi Pond Maintenance

Feeding Fish

Feed your fish just once per day to avoid overfeeding. If you overfeed your fish, this will lead to leftover food decaying in the water. This is not only going to cloud your pond water quickly but can also make the fish sick.

Spoiled food and sick fish can lead to bad odors in your pond, as well. Overall, it creates a very unpleasant experience in just about every area.

If you notice any uneaten food, do your best to remove it so you can keep your pond clean.

Don’t Let the Pond Get Crowded

Many types of fish can quickly reproduce and cause your pond to get too crowded. If your pond becomes overpopulated, this will lead to unhealthy fish.

Not only do you not want to have too many fish, but you also want to keep an eye on the plants in your pond. If there are too many plants covering the surface, it can negatively affect the oxygen levels as well as keep any sunlight from getting to the water.

Plus, you won’t be able to see your fish if there are too many plants. Then, what’s the point? A good ratio to stick by is 40 to 50 percent of plants to pond water.

Clean Your Pond Regularly

Committing to cleaning your pond daily is great, but if you can do more, then that is always better. Each time you go to admire your pond, clean out any debris you see.

The longer debris sits in water, the more time it can have to decay and ruin it. Keep your pond clean by routinely removing sticks, leaves, or anything else that may find its way into your pond.

One method to make your cleaning process more manageable is to use a net that catches plant matter and keeping it from landing in the pond.

Get the Right Equipment

We’ve already discussed the importance of having the equipment, so we won’t go over that again. However, for best results, you’ll want to make sure you’ve done your research to know what types of equipment work best for your specific pond.

Ponds come in all shapes in sizes, and so does equipment. When choosing things like pumps and filters, you’ll want to know the exact size pond you have and which piece of equipment is best for the job.

Read manufacturer instructions closely to ensure that everything will work the way it is supposed to. When cleaning your pond, take a look to make sure all of the parts are moving smoothly. Check the filtration system often so you can be sure it’s not clogged.

Keep Pond Safe From Predators

You may not be the only one who has been eyeing your pond. Unfortunately, a pond can come predators, and it is up to you to keep your fish and plants safe from outsiders.

Look out for these predators:

  • Raccoons: You probably already know that raccoons will eat just about anything, and that includes fish from your pond. 
  • Birds: Many types of birds feed on fish such as heron or owls. These predators are quick, smart, and are excellent hunters. 
  • Snakes: If you have bigger fish, you may not have to worry about snakes. However, if you have smaller goldfish, you will want to prevent snakes from finding your pond. Read this article to learn how to avoid snakes in your backyard altogether. 

Even if one of these creatures find their way to your pond, it doesn’t mean you can’t keep your fish safe.

Here are some methods to protect against predators:

  • Add Deterrents: Dogs make a great backyard companion for deterring predators. Bird dogs like labradors or spaniels are the best dogs for protection.
  • Hiding Places: If you’re planning on adding plants to your pond, you’re already a step ahead by giving your fish a place to hide. For further protection, consider adding small caves within your pond. Add any caves before adding water. The deeper you can place them, the better.
  • Floating Mesh: While floating mesh or netting is a great way to keep predators away from fish, it can take away from the pond’s beauty. However, if you’re continually having an issue with predators, this is a good last resort.
  • Decoys: Using decoys such as bird statues, fake fish, and even scarecrows can trick predators.  When using decoys, be sure to move them from time to time to keep predators from catching on. 
  • Motion Sensor: Purchase a motion sensor that sprays water when activated to scare predators. While they will most likely leave, it will at least give the fish a warning to hide.

Final Thoughts

Learning how to build a koi pond in your backyard is a rewarding experience that you’ll get to enjoy for many years to come. Knowing the right steps to take during the building process is vital to your success.

We hope after reading through this, you feel fully confident and prepared to get started with your pond.