How to Build a Koi Pond


The building of a Koi Pond can be extremely joyful as a process. You get to literally bring a marvel in nature to life in your very own backyard.

With so many variations and steps out there from many professional or expert Koi Pond builders, it’s easy to become lost.

That is why we distilled How to Build a Koi Pond into 10 very simple fundamentals.

The rest is completely open to interpretation and creativity at your leisure.

How to Build a Koi Pond: Table of Contents

1. Planning Stage
2. Excavation
3. Equipment Placement
4. Pond Liner and Underlayment
5. Adhering Pond Liners
6. Rock Formations
7. Foam or Waterfall Foam
8. Tubing, Connecting, Flex Pipes
9. Filling With Water
10. Additional Final Touches and Maintenance

In 10 easy steps, you’ll learn about the concept of How to Build a Koi Pond.

At the end, it is our goal to have you feel ready to take on a project like this, in your very own backyard.

Planning to Build a Koi Pond

When planning to build your Koi pond there are a few principles to keep in mind.

The builder needs to take note of trees, root systems, existing pipes and electrical lines. It is suggested to search and mark an area with part sun or full sun exposure for the plants and fish.

Excavating A Koi Pond

When you begin to dig out your Koi Pond area, start by outlining the Koi pond’s perimeter.

Make sure to mark off where the pond skimmer will be, where you wish to place waterfalls and pond filtration placement by using marking paint.

Now the fun begins! Here you will start the excavation process by digging tiers/shelves.

At the bottom tier, you should be at least 4 feet deep to accommodate Koi fish over the winter.

Placing Koi Pond Equipment

Place and backfill both the koi pond skimmer and the pond spillway.

First, try to make logical sense of the layout in order to place your flex pipe, and the pressurized filter.

The pressurized filter is usually placed behind the waterfalls.

Koi Pond Underlayment and Pond Liner

Line your entire Koi pond and waterfall area with underlayment followed by 45 mil EPDM Pond Liner.

The basic concept here is that the underlayment is placed FIRST, followed by the liner on top.

Take care here to make sure the liner extends beyond the perimeter by 1 foot or so. This will allow for settling earth and rockery over winter.

Finally, extend the Koi pond liner BEHIND your waterfall. This will adequately keep water from spilling or dashing out.

Adhering Pond Liners

Begin this step by taking the pond liner and attach it using lap sealant to the pond skimmer.

The bolts should be provided with the pond skimmer. Next, attach the pond liner to up-flow spillway.

Meaning, lap sealant/nuts and bolts. Additionally or alternatively, you can have the pond liner come in behind the spillway if you do not have a faceplate.

Placing Rock Formations

Now is the time to start placing your rockery or stone formations. You need to begin with the largest pieces of rock followed by the smaller ones to work towards the edges.

Edge stones should be worked into the first shelf of the koi pond and also on the top surface to hold the pond liner firmly in place.

Foam in Your Koi Pond Stream

By using waterfall foam in the stream near the adjacent spillway, or between the rocks, you’ll be able to precent water from flowing and being lost through the stones as it moves down to the pond epicenter.

Connecting Pipes in Your Koi Pond

Begin this phase by connecting your pond skimmer pump to the spillway using a PVC Flex pipe.

Make sure to place the pump in the back of the pond skimmer here.

Continue connecting a solids handling pump to the pressure filter and then from the pressure filter back to the spillway.

You can connect from the pressure filter back to the pond directly if you’d like!

Filling Your Koi Pond

Everyone really enjoys this step in the process! Start by filling your Koi Pond with water and add dechlorinator as a water prep.

Then add the starter for beneficial bacteria.

Make sure to run the pumps and filtration to ensure everything is running smoothly.

Final Steps on How to Build a Koi Pond

Place any plants around the Koi pond in order to re-create a more natural environment.

You may be wondering about when you can add wildlife, right?

You won’t have to wait too long, at this stage both, Koi fish and plant life can be added a few days after filling.

A good rule of thumb is to make sure the water temperature is warmed appropriately.

Pond aeration should be added as you a place the fish into the pond, lighting of any kind that is approved for outdoor or pond use can be added whenever you like.