Pond Design

Pond Construction Guidelines

The following provides a quick summary or overview of the considerations when you are planning or designing your first or subsequent Koi pond.

Location of your pond

This is the first and most important consideration since it will drive the design of the rest of the pond. Typically, this will be considered together with the size, shape and style of the pond. There may be constraints such as existing layout of your house, environment and other factors.  Your personal reasons for having a Koi pond will be key considerations. These could include:

  • A feature or place in the house for relaxation. In this case, locate the pond close to your house where you can view your Koi easily.
  • To keep Koi as a hobby
  • To fit or complement the overall building or house design and to add to its aesthetics.
  • Geomancy or Feng Shui, i.e. to bring good luck to you and your family. Consult a Feng Shui Master or geomancer if this is a key reason.
  • To also keep aquatic plants or water gardening. For these, the pond must be located where it will receive at least 4 hours of direct sunlight per day. More if you want your water lilies to flower regularly.
  • As a garden feature.

Style or shape of your pond

A formal pond is one with standard geometric shape (rectangle, square, circle or ellipse).  A formal pond will look best in a formal setting such as against a tiled up patio, against a house wall or at the centre of a large open lawn. An informal pond is one with a shape that appears to naturally form. Common shape would be kidney shape or any irregular shape that can fit into a garden setting. Formal or informal is a matter of personal preferences.

Size and depth, volume

You will have to consider the koi environment needs when deciding the size, depth and volume of the pond.

Pond Construction Material

There are typically 3 options – concrete pond or using a pond liner or use a pre-formed bowl. For large ponds in South-East Asia, most Koi ponds are built using reinforced concrete. Smaller ponds will use a pre-formed fibreglass or plastic bowl or shell.

For concrete ponds, it would be essential to coat the surface with special epoxy sealant paint.

Filter design or filtration system

The filtration system is the most important element of a Koi pond. Key considerations would be

  • Build (custom designed in-ground filter) or Buy (commercially designed external filtration systems)
  • Size of the filter, number of compartments, media type
  • Location of your filter
  • Bottom drains

The water quality would depend heavily on the design of filtration system and it will determine the health of your Koi, and overall beauty of the Koi pond and its surroundings. A good filter system will also make filter maintenance and pond maintenance easy.


This is often planned and selected together with the filtration system. If the filter is the “kidney” of the pond, the pumps are its heart. Selection of the right pumps to use is just as important as the filter design as it will affect the water flow rate, effectiveness of the filter system and workings of water features, especially waterfall or fountain.

Aeration and water features

Koi needs oxygen and so does the bacteria in the biological filter. Besides the natural absorption that occurs at the pond water surface, any ways to agitate the water artificially will increase the oxygen absorption by the pond water. Consider having a waterfall for aesthetic reason, as well as for pond aeration.  Waterfalls are ideal for informal ponds. Plants and rocks formation can create a beautiful natural setting. For formal ponds, consider having a fountain. Such water features also create the soothing sounds of gurgling water in the home.

Overflow pipe

Don’t forget this small but essential feature. It allows excess water, e.g. during heavy rain, to overflow into a drain.

Surface skimmer

Every pond ought to have a way to remove floating debris from the water surface. Dust, oil, protein scum, and small floating debris (insects, dead leaves) can be removed with a surface skimmer device.

Bottom drains

This is important feature for your pond and in-ground filter system for easy maintenance.

Water plants

Whether to include water plants in your Koi pond or not would depends on the style and shape of your pond. The overall design and layout of your pond will need to be planned carefully, together with the types and species of water plants that are suitable for Koi pond.


The edging of your pond could serve a few purposes:

  • Prevent surface water runoff during rain from entering your pond.
  • aesthetics
  • safety barrier
  • platform for feeding and netting or capturing your Koi

If your pond is an informal garden pond, the edging is important as you would want it to blend with the rest of the garden or setting.

Platform or place for Koi feeding and capturing or netting of your Koi

It is good to consider where you would stand to view and/or feed or catch your Koi safely. Avoid protrusions (e.g. overflow pipe or skimmer) or even water plants near the place where you intend to feed your Koi as they may feed in frenzy and knock themselves against such protrusions.

UV Light filter

UV Light filter may be useful to as a means to control bacteria or parasites, kill germs and sterilise the pond water.

Water supply

Easy source of water supply must be provided near your pond for water changes and replacement of water lost through evaporation. Have a tap or faucet located next to the pond. Better still; build a water inlet pipe directly into the pond.

Power source for pumps

Best is to have multiple power sources, with individual circuit breakers and isolators for each pump that you have. That way, a single pump failure would not knock out all the pumps and stop water circulation and aeration.

What are Koi’s environmental needs?

Ornamental Koi are mostly bred in Japan and shipped to rest of the world. Many years of selective breeding had led to development of various colourful varieties of Koi but all will need the same water requirements. They are relatively hardy fish and can tolerate poor water conditions but not for prolonged periods. If you are serious about Koi keeping, then continual good water quality is must to maintain your Living Jewels at their peak condition.


Koi can grow to as large as 1 metre in length, although most Koi sold are young Koi and averages from 20 cm to about 50 cm. Koi need space to thrive and some Koi experts have claimed that growth rate is proportional to pond size and volume of water per Koi. Just like in aquarium fish keeping, a larger volume of water or pond would also provides more stability in the water condition. Often, this is limited by available space for the pond and not by cost.

Oxygen level

Koi needs oxygen and so does the bacteria in the biological filter. Dissolved Oxygen level of 8 mg/litre in water temperature of about 25 deg C is almost ideal since it is almost at saturation point. Note also the plants (including algae) in the water also uses oxygen at night. Plants take in carbon dioxide and produce oxygen only in the day, during photosynthesis.


There is a need to keep the water cool in hot, sunny India where the daily temperature ranges from 25 deg C at night to 34 deg C in the day. Warmer water does not carry oxygen as well as cooler water. In any case, some shade would be good for the Koi. I have read about Koi getting sun-burn from prolong exposure to direct sunlight.

Pond Depth

Pond depth should ideally be at least 1.2 meter or about 4 feet. A deeper pond is good for the Koi growth but one has to be mindful of the proportion of the depth versus size of the pond. You find the Divine Ratio an interesting read (http://goldennumber.net/architecture.htm) but this is not a must-have pond building requirement! Also, a deeper pond would allow for greater pond volume per unit pond surface area. Pond surface area is usually limited by the space available in our home or garden. A deeper pond would also help keeps the water cooler in hot, sunny weather.

pH level

pH is a measure of the acidic or basic (alkaline) nature of a solution. Normal tap water or fresh water should have PH level of 7. Water with a lower PH level is deemed acidic while alkaline water would have higher pH. Chalk, limestone, coral or seashells dissolved in water will produce higher pH. Low pH or sudden drop in pH level kills Koi and many other fishes. It is generally better to have pond water for Koi at with slightly higher pH (7.4 is ideal. Not more than 8.0).

Ammonia, Nitrite and Nitrate

Fish produces ammonia as a waste product and a good filter system must be provided to remove this ammonia from the water. If a biological filter is used, the bacterial in the filter will convert the ammonia to nitrite and then from nitrite to nitrate. Nitrate is relatively less harmful to fish and Koi than ammonia or nitrite. Ideal levels of ammonia and nitrite should be zero or near zero and this can be achieved using a good biological filter system. Nitrate level should be less than 25 mg/litre. The only way to reduce nitrate is through partial water changes and also use of water plants. Nitrate is commonly found in garden fertilisers (the N in the NPK fertiliser).