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News and articles about products used for the containment of water and the use of flexible rubber liners for many environmentally enhancing projects.

Essential tips on KOI pond design and pond liner installation

Koi fish are bred especially for purpose built ornamental ponds. Breeding of these fish has been successfully mastered and perfected by the Japanese over many, many years. From all this history on Koi keeping we know that they need specifically designed ponds which have depth and vertical sides to limit sudden temperature fluctuations and to provide the ideal habitat in which these fish can thrive. To be successful at keeping Koi the conditions within the pond need to be right.

The first step is to do as much research on Koi keeping in the UK as possible and on Koi pond designs. When planning your Koi project remember that the most important addition to a KOi pond is the filtration system. Koi produce a huge amount of waste matter that needs filtering out of the water before decomposing resulting in an increase in nutrient levels thereby affecting the water quality. Koi are hardy and easy to keep if their surrounding conditions are right.

Things to consider before designing a Koi pond

  • Keeping Koi is an expensive hobby so it is advisable to do all your research and cost up your project before you plunge your spade into the ground and start digging.
  • Koi, at their full potential size need to have space to move about and exercise. This means that your pond design needs to be as big as space will allow. Small ponds will stunt their growth. The average Koi pond size is 25 feet long by 13 feet wide and a depth of 4 feet. This size will accommodate up to twenty mature Koi offering plenty of room to move about. A minimum size pond should be no less than one that holds 1200 gallons (5500 litres) of water.
  • A pond holding 1200 gallons of water can accommodate no more than 5 mature Koi fish. Volume is calculated by measuring pond length x width x depth = feet x 7.5 = gallons. 
  • Fish are cold blooded and will match the temperature of their surroundings. So, the bigger a pond, the less the water will fluctuate in temperature and a deeper pond is less likely to ice over in the winter. Sudden changes in temperature affect the physical health of Koi.
  • A filter system is an absolute necessity to keep the water clean and of a healthy quality. A bottom drain is worthwhile including in your build for times when you need to drain water as part of pond maintenance.
  • The attractive bright colours of Koi make them visible prey to predators such as heron and other big birds so it is advisable to install netting or a form of deterrent over your pond.

About the Koi pond design

A simple shape allows for good water circulation

The most cost effective way to build a pond is to line with a high quality rubber pond liner such as EPDM or Butyl. To calculate how much pond liner to order you will need to measure the longest length, the widest width and the depth taken at the deepest point. Add to that a 30cm overlay which is needed to secure the pond liner in place. 

Length + (2 x depth) + 30cm overlap.

Mark out the design of your pond to exact dimensions using rope, chalk or spray paint. Before you start digging check that you are 100% happy with the location, size and shape of the pond you are about to build. 

Dig a trench for the bottom drain pipe to run to where the filtration system will be placed.

Vertical sided Koi pond lined with rubber pond liner


Install over a Geotextile protective underlay with the minimal number of creases and folds to avoid debris getting trapped inside them leading to water quality issues. You can fix down the folds at the corners using mastic tape. Another option is to call on the services of RDL who have the expertise in heat bond the liner to the contours of the pond to avoid folds and creases. A rubber EPDM pond liner can be completely fabricated on site using hot air machines to create a smooth finish in keeping with the formal pond design.

Their colours, graceful swimming and gregarious nature make Koi keeping a very rewarding hobby. A well designed Koi pond will add style and beauty to any garden therefore it is worth the initial research to build one you will love and one robust enough to last the average life time of Koi who will live to 35 years if the pond they are accommodate in offers the best quality surroundings.

To discuss your Koi pond design, build and pond liner or box-welded pond liner installation, contact RDL today on 

Tel: +44 (0)1908 556041

Email: info@russetts.co.uk

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