Tips for Building a Koi Pond

All you need to know about building a koi pond.

Koi keeping is an exciting hobby that adds excitement to your life and brightens up your garden. The sound of running water and the sight of colourful koi creates peace and tranquillity in just about any space. With Covid-19, we are all spending more time at home in a safer environment, so now is the best time for building a koi pond at home and do some gardening. Koi make wonderful pets, and until you have experienced keeping them it is hard to explain the pleasure that they will bring you.

Koi are far more intelligent than you may think, and before you know it you will be handfeeding them and giving them all nicknames. They can see and smell and will learn your body shape, and whoever feeds them the most will be their best friend. Food is definitely their love language! Below I have listed some points to consider when building your koi pond:

Aesthetic Considerations

Every pond is unique, built to suit a particular person, their garden and their approach to the hobby. Design Choose a design that will suit both the home’s architecture and the garden’s design:

  • Classical: A classical pond is formal and symmetrical. It can be raised above ground and is sometimes paved with geometric tiling. Planting is usually done in containers.
  • Informal: An informal pond is more natural in appearance, with curves and a free-flowing shape. They are often decorated with items such as sleepers, rocks and tropical plants like tree ferns and palms.
  • Oriental minimalism: These Asian-inspired ponds are often surrounded by bonsai, raked gravel, bridges, large rocks, oriental lamps, and plants like conifers, Japanese maples and azaleas.

It is possible to incorporate a marsh garden/ stream into your pond setup, planted with water plants to help to control nitrate levels. Some koi love to eat aquatic plants, so I usually recommended that water plants are grown in a separate plant area. If you want to grow water lilies, it is a good idea to pot them up in special mesh planters that protect them from destructive koi.

Plants for Water Gardens

  • Arum lilies (Zantedeschia aethiopica)
  • Waterblommetjie (Aponogeton distachyos)
  • Blue lotus (Nymphaea nouchali var. caerulea)
  • Cape bulrush (Typha capensis)
  • Umbrella grass (Cyperus alternifolius)
  • Paper reed or papyrus (Cyperus papyrus)
  • Blue ginger (Dichorisandra thyrsiflora)
  • Lobster claws (Heliconia)
  • Impatiens Louisiana iris
  • New Zealand flax (Phormium tenax)
  • Water lily (Nymphaea)
  • Ferns
  • Miniature bamboo
  • Various grasses


Here are some tips on where to place your pond:

  • Close enough to your house to enjoy the koi.
  • Allow easy access to the pond – don’t put rocks around the entire pond, and leave a flat area for access. If you need to catch your koi, you need somewhere to stand.
  • Space to view and manage your collection.
  • Space for a filter unit. (Never forget this one).
  • Include a place for seating and relaxation.
  • Consider a gazebo, patio or thatched roof for cover.
  • Incorporate decking to create an entertainment area.
  • Part sun/part shade is best. If koi get too much sun, they can develop skin cancer.


  • Self-analysis: Decide what you want out of a pond. Do you just want a garden water feature, a small pond with a few fish, or do you anticipate becoming an obsessive koi fanatic? This will determine how much space, time and money to invest in the project.
  • Proportion: Match the size of the pond to the setting and size of your garden. If it is too small it will look cramped and insignificant.
  • Place the pond away from trees with very small leaves.
  • Build a bigger pond than you think you will need, as koi grow quickly.
  • It is cheapest to build a pond properly the first time, so build as large as you can afford, within the space allocated
  • Depth: A pond should be between 1.2 m and 1.5 – 2 m deep. If it is too shallow the water temperature will fluctuate, which isn’t good for the fish.


Get expert advice on your particular requirements before you do anything!

Materials: Ponds can be constructed out of gunite, bricks/blocks, concrete, vinyl liners or a fibreglass shell.


Filtration is key, and you can never over-filter. A combination of mechanical and biological filters is the most effective solution.

A. Mechanical filter

  • Incorporate a bottom drain with 110 mm outlets set at the bottom of a sloping floor. The filter should feature a settlement chamber to trap solids.
  • A weir skims the water’s surface of leaves.

B. Biological filter

  • A bio-filter is necessary no matter what kind of fish are to be kept. It uses beneficial bacteria to remove harmful chemicals from the water.
  • Size of filter depends on site, volume of water and number of fish.
  • The filter should operate 24-hours a day to ensure proper filtration, and should filter the total volume every two hours.
  • A filter also oxygenates the water.
  • You will need to perform regular flushing of waste from the filter.


External lights aimed down at the pond are better than lights submersed in the pond. You can also use spotlights to highlight feature plants. Choose LED lighting for low electricity usage.

Safety NB

  • Childproof the pond
  • Remember: depth is no guarantee of safety – a child can drown in extremely shallow water.
  • Use a proper swimming pool net that can support the weight of a child.

Angela Beckx of Koi@Jungle can be contacted on 031 209 8781, or visit www.koiatjungle.co.za.

The Gardener