There isn’t one way to build a Koi Pond. It’s a process that can be done through various methods, at different budgets resulting in different sizes and shapes.

Basically, no two Koi Ponds are alike. However, there are certain aspects all Koi Ponds must have in common in order to function properly and provide the right conditions for the fish to thrive and be happy and healthy, the most crucial ones being:

  • A pond skimmer
  • A back-washable biological filter
  • A pump
  • A bottom drain
  • A bottom drain pre-filter
  • An aeration system
  • Minimum depth of at least 4′
  • No sharp objects that could harm koi
  • No planted aquatics 

So, before getting started on the actual step-by-step guide on how to build a Koi Pond, let’s first go through some basics that I believe are necessary to know before making any decisions

How Much Do Koi Cost?

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Just like any breed, Koi fish could go from 20 bucks to hundreds of thousands of dollars, depending on the skin, size, shape, quality and many other factors.

But the good news is, they breed like crazy! So you don’t really need much fish to start.

If you’re looking to save some extra money, don’t go to a pet or garden supply store for the Koi, as they charge more than would a breeder at a Koi farm for example.

They are often in better health and you get a chance to speak to the breeder and learn more about the different breeds and varieties of Koi fish.

How Large Should The Pond Be?

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Ideally, a Koi Pond should be no less than 1500 gallons, that is a minimum of 10 feet (3 m) long by 6,5 feet (2 m) wide, with a depth of 3-4 feet (0.91–1.22 m).

This is a popular size for backyard hobby Koi fish ponds. You can expect it to house you about 10 mature fish, with enough space for each one of them to move about and for the pond not to look congested.

Now that you have a general idea of what your pond measurements should be and where you can get good quality Koi fish for the best price, let’s discover the 8 steps that will guide you throughout the pond building process:

Step 1: Forward Planning

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When deciding on your pond’s placement, you must take into consideration any obstacle that might hinder the process and cause you trouble once the construction works would have begun, trees with heavy root systems and electrical lines should be avoided at all costs.

Make sure the site is accessible and would fit all the materials you will need for construction.

Also, since you’re planning to keep koi, the placement of the pond should be fully or partially exposed to the sun, so choose wisely.

Step 2: Design Your Pond

Draw a rough sketch of how you imagine the pond would be, try to come up with as many designs as you can, to have enough to choose from for your final plan.

Don’t hesitate to show it to others and ask for their opinions and advice, you never know where inspiration could come from.

Step 3: Outline Your Project

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Before beginning any construction work, make sure to clear the site of any vegetation or furniture that might be in the way. With a rope, spray paint or a garden hose, start by mapping out your design drawing on the ground in real scale.

You can use these dimensions to get a glimpse of what you’re going to build prior to digging. Make sure to also mark where components of the pond like the skimmer, falls and filtration will be placed.

It’s an important step as it enables you to visualize and build anticipation for your project.

Step 4: Labor Work – Constructing The Pond

Begin excavation by digging tiers. The bottom tier should be at least 3 to 4 feet deep to accommodate fish over winter.

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You can use a sturdy shovel, or, if you want to get the work done faster and more easily, you can rent a small excavator from your local rental place and start digging.

It’s extremely easy to operate, and will also allow you to re-locate your soil by loading its wheelbarrows. In which case, the same soil could be used to cover the pond skimmer, pre-filter, aeration and other installation you don’t want in your aesthetics. Isn’t that amazing?

Step 5: Place Your Equipment

Set up the filtration system box right next to the koi pond. Dig it into the ground slightly. Install the individual parts in the pond as per the installation directions.

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Place and backfill both the skimmer and the spillway. Roughout the placement of the flex pipe, and the pressurized filter (usually in behind the falls).

Step 6: Line Your Pond

You can purchase a tough plastic or rubber pond liner, preferably a one-piece to prevent the pond from leaking, from any home improvement or landscaping supplier.

Follow the manufacturer’s directions to install the liner. Have some people help you roll it out over the pond while making sure it overlaps the edges by at least 3 feet so that it can be secured in place.

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Place large stones and rocks over the liner to cover it completely, leaving only about 1 foot of the liner exposed, this will help prevent rainwater from getting into the pond.

For some extra protection, you can dig a 3-inch-high ridge around the edge of the rocks while making sure that the liner reaches onto the ridge.

Step 7: Add The Water

Using a garden hose, fill the pond with water and add de-chlorinator and starter beneficial bacteria if the water isn’t fresh. Run pumps and filtration to make sure everything runs smoothly.

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Run the necessary water quality tests (pH, KH, Ammonia and Nitrite) to see if your pond is ready to host the fish, make sure to run the same tests again a day or two after the fish are in the pond.

Note that Koi thrive best in a temperature around 18 °C (65 °F), so you need to measure the temperature of your pond regularly with a thermometer.

Step 8: Add The Koi

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Once the water temperature is adequate, usually after a few days, you can proceed to add the Koi and plants. Give the fish some time to get used to the pond water and adjust to the new environment before taking it out of its plastic bag.

Don’t leave it under direct sunlight to prevent the koi from overheating, simply place a towel over the bag if there’s no shade.  

And voilà – your brand new Koi Pond is complete!

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