Introduction

Firstly, it must be said that employing the services of an experienced, professional contractor will usually result in a high quality Koi pond, although many previously inexperienced Koi keepers have successfully constructed 4–5m3 ponds in as little as three or four days. However, if you do decide to do it yourselves, the first step in the process of pond construction is to consider safety. Even with fences and pond covers, there is no such thing as a completely safe pond, so a pond should not be installed where there is any chance of young children gaining unsupervised access.

The next step is to produce a detailed sketch or plan of the existing garden, with details such as gradients, soil types, underground sewage, electrics or gas pipes, the location of trees, shrubs, sheds, pathways or fence lines. Use the sketch as a blueprint for considering a range of potential locations and designs, influenced by all the above factors, before making the final decision.

As a general rule, bigger ponds provide the stable aquatic environment required by Koi and many keepers suggest that ponds should be no less than 1m deep. It is often considered that the design of the pond should also reflect the design of the surrounding garden. A formal garden that’s broadly symmetrical suits a formal, symmetrical pond, while an informal garden might suit a more informal, ’wildlife’ pond. Many Koi keepers also apply a Chinese, Japanese or even a traditional English theme to their garden and pond.
 

Written by Craig Baldwin

Photo courtesy of Stuart Scott

Liner ponds

Liner ponds are often regarded as the simplest form of pond construction and offer the potential of quickly lining ponds of almost any size and shape. Butyl rubber is traditionally recognised as the toughest and most flexible form of pond liner – they can be made from a range of materials and come with a long guarantee. While pond liners are quick and easy to install, they do require some experience to prevent unsightly creases, and they are also more likely to be damaged and holed compared to other types of pond.

Installation of a liner pond often benefits from the construction of a concrete collar in the shape of the pond before any excavation takes place. The collar will help to stabilise the soil, provide a stable foundation for capping stones and ensure that the edge of the pond remains perfectly level. Once excavated, line the pond with a protective pre-liner before adding the pond liner on top, then slowly fill the pond and gradually pull out any creases.

The internal dimensions of the excavated pond dictate the size of liner. The length of liner required is equivalent to the maximum length of the pond plus twice the maximum depth, plus an overlap of approximately 50cm. The overlap helps to hold the liner in place by trapping it between the concrete ring and the capping stone.

The installation of side drains or bottom drains required for gravity-fed filters is surprisingly simple. Drains intended for liner ponds contain a collar that locks them in place and while they are simple to fit, the process of cutting a hole in the liner to fit the drain is always a hair-raising moment!
 

Written by Craig Baldwin

Block-built ponds

Block-built ponds are the Rolls Royce of Koi ponds, due to the variety of shapes and sizes available, their shear ruggedness and longevity. However, the high costs and specialist skills required to complete these ponds tends to limit their application to more experienced Koi keepers.

Once the hole has been excavated, the first step in constructing a block-built pond is to install a concrete slab as the base, before the walls are built from standard pierced concrete blocks. Many ponds require the installation of reinforcing steel rods to stabilise the physical structure of this concrete shell.

Many Koi keepers choose to line the concrete shell with a box-welded liner or seal it with a waterproof sealant, many regard sealing or skimming the surface of the shell with hard-wearing fibreglass as the ultimate Koi pond. While a fibreglass skim does provide a hard-wearing surface, it can prove to be an expensive process and almost certainly requires the services of an experienced contractor to achieve an acceptable finish.

The rigid concrete shell provides a stable framework for the installation of any pipework or drains. However, obtaining a watertight seal around any intrusions into this concrete shell can be tricky. Unlike liner ponds, installing new drains or fittings into a block-built pond can be very difficult and is always best avoided by a undertaking a thorough planning process before the construction is started.
 

Written by Craig Baldwin

Photo courtesy of Simon Kelly

Pipework

Pipework is required to feed waste-laden water from the pond into the filter and then transport the filtered water back into the pond. The choice of pipework is a vital element in ensuring the safe and effective maintenance of your pond.

Flexible hose is the cheapest and most versatile type of pipework, and is now available in long lengths of a variety of pipe diameters. It can easily be bent to cope with corners, without impacting upon flow velocity, although it can be difficult to fit it with the valves and accessories of complex Koi filtration systems.

So flexible hoses are most suitable for pump-fed filtration systems, where the need to install additional valves or fittings is limited. Rigid pipework is usually the most effective for gravity-fed filters where solvent-weld rigid pipework enables stronger and cleaner joints for drains and accessories such as UV clarifiers, and pump or filter fittings.

The velocity of water delivered by a section of pipe over a period of time is affected by a number of factors. While the pump is probably the biggest factor influencing waterflow within a pipe, it’s also influenced by the diameter, length and height up to which a section of pipe is expected to deliver water.

As a general rule of thumb, the output of a section of pipe will be reduced as the diameter of pipe is reduced, as the velocity of water passed through the pipe is reduced, as the length of pipe is increased and as the height up to which that pipe is expected to deliver the water is increased. While it is possible to calculate the impact of each of these factors, merely being aware of the impact of them will enable Koi keepers to reduce their impact and perhaps improve the performance of filters.

Written by Craig Baldwin

Photo courtesy of Keith Holmes