How To Build A Koi Pond UK

Building a koi pond on your premises adds value to the property and creates a serene and peaceful atmosphere. Koi fish are symbols of wealth and status in Japan but are popular worldwide.

Building a koi pond in the UK, you will need space in a secluded area away from trees. The koi pond will have to be at least 3 feet deep and be built under a greenhouse to protect the koi from extremely low temperatures. You will need materials such as rocks, underlayment, and a pond liner.

Building a koi pond will follow the same basic principles as building a swimming pool. You would need the same basic materials except for the sealant or liner, which must be marine grade. Marine-grade liner is safe to use with fish. Let us look at how you can build a koi pond in the UK.

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Materials Needed To Build A Koi Pond In The UK

Before getting the materials for your koi pond, you’ll need to measure how big you’d like the koi pond to be, how deep, and depending on the weather. If you live in a place where it snows or is very cold, you’ll need to build a greenhouse around the koi pond if the pond is not at least 3-5 feet. Deep enough not to freeze completely and still provide oxygen.

To prepare for the pond site, you’ll need:

  • Spray paint or chalk
  • Garden hose or rope
  • Rounded shovel
  • Square spade
  • Measuring tape
  • Wheelbarrow
  • Rake
  • Level
  • A straight board long enough to distance the width and length of the pond
  • Sand

To build the koi pond, you’ll need:

  • A pond liner
  • Underlayment
  • A pump
  • Rocks
  • A filter
  • Heater
  • Pipes, tubing, and fittings
  • Skimmer
  • Lighting
  • Material to finish pond edge
  • Water

Now that you have all your pond materials, you’ll need to know how deep it will be and if it’s too cold for the pond to be out in the open. If that’s the case, you’ll need a greenhouse, too, and then more materials for the greenhouse. If not, you’re about set and ready to start building the pond.

Where Can I Get Materials To Build My Koi Pond In The UK

Finding materials depend on what city you live in and what type of pond you’re building, the size of the pond, and the koi you’re planning on having in the pond. You should be able to find food, plants, and sand at about any pet store in your local area.

You’ll need to go to a hardware store and pick up supplies for the pond itself. If you need a greenhouse, you can find pre-fabricated greenhouses at nurseries. You may also find supplies on amazon or at a store specializing in koi supplies.

The type of pond you’re looking to build will determine where you’ll have to go to get your supplies and what type of supplies you’ll need.

What temperatures Are Best For Koi

To maintain happy and healthy koi, you need to maintain the temperature of your pond. The best temperature for your koi is between 65 and 77 degrees Fahrenheit (18 to 24 degrees Celsius).

A koi fish’s metabolism reacts to the water temperature that they live in. The colder the water, the less they’ll eat. Even tho koi can survive in temperatures from 35 to 85 degrees Fahrenheit.

It’s best to stabilize their water temperature, even the slightest change in water temperature can impact your koi. Keeping a thermometer in the pond water will help you keep an eye on the temperature of the water throughout the seasons and the day.

Koi can survive for a while in water up to 85 degrees Fahrenheit. This is already too warm for most fish and also many aquatic plants. When the water temperature rises, it has less dissolved oxygen, while the ammonia levels rise and will become toxic to the koi and all the pond life.

 Here are a few tips to cool your pond temperature down:

  • Create some shade over the pond as soon as possible
  • Change 20% of the total pond water. Doing this gradually to lower the temperature will help and not cause shock to your koi.
  • Add an air pump. Adding an air pump will create more than enough turbulence to ensure that more oxygen will be dissolved in the water.

How Deep Should My Koi Pond Be

Any koi pond should be a minimum of 3 feet deep. No part of the pond should be less than 2 feet deep. If your pond is 2 feet deep or less, it’s an open invitation to predators and may overcrowd the fish.

If the pond is too deep, the bottom of the pond will have insufficient access to oxygen and sunlight, which isn’t suitable for the koi. The pond should always be longer than its depth. The length should always be about 1.2 – 1 times its depth.

For example, if the pond is 4 feet deep, the length of the surface should be about 8 feet. With this ratio, the water temperature will stabilize, and enough space will be provided for the koi to roam freely.

If you plan on having jumbo koi, the depth of 6-8 feet should be good. Jumbo koi can grow from anything between 34 to 36 inches (86 to 91 cm). They naturally swim up and down to look for food and get exercise, so they need a lot of space to grow properly and maintain health.

The deeper ponds are more expensive to maintain since you’ll need to invest in more filters and pumps to ensure the pond’s bottom receives sufficient fresh water and oxygen. There will also be a more significant volume of water requiring more energy for proper filtration and oxygenation.

Depending on the depth, length, and width of your pond will determine how many pumps and filters you’ll need.

How Many Koi Fish Can I Put In My Pond

There should be 227 liters (50 gallons) of water per adult koi. If you were to have 30 koi fish, 6 inches long, there should be around 6819 liters (1500 gallons) in your pond.

This will keep the fish happy and give them enough space to roam around and be healthy. If your koi don’t have enough space to roam around, they can get sick and won’t be happy or be able to get the exercise they need.

If your fish is 18 inches, you’ll need to keep fewer koi in the pond. You’ll know when to take some koi out when they aren’t swimming as much in a more relaxed way and how crowded they look, even if the water quality is fine.


Building a koi pond in the UK does not come without some challenges, but it is worth the effort to enjoy watching your beautiful koi grow. Koi fish are known to develop a keen relationship with their owners and can live quite long if they are happy.

To build the best koi pond for your garden, we suggest you follow our guidelines on how to build a koi pond in the UK.


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