5000 Gallon Pond


I was contacted to help design and build a koi pond in fitting with the proposed landscaping.

There was limited room for a filtration system as well as pump room for uv, heater etc.

The client did not want to see any pipes or large areas taken up by filtration.

The client was also new to the hobby and wanted the pond easily managed.


The size of the pond is the maximum that a single bottom drain would allow and also the area designated for the filtration


The construction of the walls and final finishing was done by buliders and joiners. I was to install the pipes, equipment, fibreglass and to ensure the pond was built correctly.

The pond was excavated and a first base cast then I installed the bottom drain, air pipe and 4" pipes for the filtration. A second base was then cast to encase the pipework.


The waste from the filter was connected to the main sewer and construction commenced on the pond and filter walls.

The filter was to be built out of concrete blocks and a standard width of 50cm with the length around 2.4 metres. As of yet water level had not been determined so the filter was constructed to enable a varying water level.

The decking build is now underway and the first stage of fibreglassing has been done but then snow the following day has stopped work. The skimmer has also been raised and filled with foam now that the pond water level has been determined.

The fibreglassing has been applied to insulation boards for better thermal properties as the pond will be heated in winter.

While the weather is bad work is carried out on the skimmer line. All the equipment was first built onto a plywood board then installed in the outside basement area of the house. The small pipe at the bottom of the picture is the air line from the bottom drain which has a non return valve and will then be connected to a 40 lpm air pump.

The weather has now picked up and the pond is finished quickly. The fibreglassed has been finished and the filtration media has been added. The pond was filled and all equipment turned on and tested. The koi will now be added once the decking has been completely finished. The water depth in the filter is 70cm with 3 rows of brushes attached to make a box and 3 japanese matting cartridges measuring 50cm x 35cm x 75cm. There are rubber membrane air diffusers between each cartridge which provide the necessary water disturbance to ensure all the surfaces are used for bacteria. The filter takes 30 seconds to discharge to sewer then another 30 seconds to rine the brushes of larger debris with the hose. Most of the debris in the brushes is flushed out when the discharge begins as all the water has to backflush to get to the waste exit. This filtration system is the best available for both the novice and experienced koi keeper. This system is now available as a prebuilt box for easier installation, please enquire for details.

The skimmer water return feeds a 2 metre weir box. 12 high class japanese koi purchased from myself have now been added to the pond. The pond showed no ammonia readings and nitrite is present during the first 8 weeks. The koi look fantastic and the client is happy with the results and ease of cleaning of the filtration system.  The finished landscaping has been carried out to high standard and you would never know there was a filter system underneath the 60cm wide walkway.