Pond Construction

Koi Pond Construction

Method: Gravity Fed – Pump Return

This method is the preferred method by many Koi keepers. It involves a filter system which is sited level with the pond and fed with pond water via a bottom drain which is fitted in to the base of the pond at time of construction. Known as “gravity fed” meaning the water from the pond enters the filter system via the bottom drain and 4” pipe. The water then passes through the different stages of filtration before being pumped back to the pond via an external pond pump. With this method of operation, the water level in the pond will be at the same level as the water level inside the filter system.

Koi produce a lot of solid waste, so by allowing the pond water which contains the suspended fish waste to flow in to the mechanical stage of the filtration system via the 4” pipe the waste can be trapped and settled out of the water ensuring the waste does not enter the biological stage. If the solid fish waste is allowed to enter the biological stage of the filter it would inhibit the growth of the live bacteria on the filter media as the waste reduces the surface area the bacteria can colonise.

Usually Koi ponds are larger in size than garden ponds so require a stronger method of construction to support the larger volume of water contained within the pond. A concrete base and concrete block walls are usual for construction which are then rendered and then waterproofed by fibreglass. If fibreglass is too expensive a rubber liner or PVC liner can be used on top of the render, this will give satisfactory results but certainly not a preferred method, only a cost saving method.

Conclusion: Concrete construction is far more expensive than a traditional pond construction using a liner laid on sand and underlay but offers a far superior pond that will last many, many years.

Garden Pond Construction

Method: Pump Fed – Gravity Return

It is usual for most Koi keepers that go on to build a gravity fed pond to have previously had a pump fed pond. The method of construction is quicker and cheaper than gravity fed, but the end results are in no way as good. A pump fed pond involves a submersible pond pump sited in the pond which pumps pond water to a filter system which is placed higher than the edge of the pond. The water enters the filter system by the pump and exits the filter via a large diameter pipe, usually 2” or 3” which allows the water to return back to the pond by gravity.

There are many disadvantages of this system which should be considered when planning to build a Koi pond. The main disadvantages are, the filter system will be visible above ground and may look unsightly, the large diameter pipe can be hard to hide and can also look unsightly. The biggest disadvantage of this method has to be without doubt the pump sited in the pond. By pumping the pond water which includes the suspended solid fish waste the pump impellor will break down the solid waste in to very small particles. These particles which are very difficult to trap out in the mechanical stage of the filter enter the biological stage and clog the filter media which in turn inhibits the growth of the live bacteria.

By breaking down the larger particles and turning them in to small particles the pond can then suffer from suspended particle related problems and poor water clarity. Suspended particle problems that cause poor water clarity can be difficult to solve.

Most pump fed Koi ponds are constructed by digging a hole in the ground and lining the hole with a protective underlay and sand then placing a waterproof rubber liner or PVC liner on top. This method of construction is quick and cost effective and a really nice looking pond can be achieved. Serious Koi keepers may well steer clear of this method but for gardeners, ornamental fish keepers and standard Koi keepers this method works well especially on a tighter budget.

Conclusion: A pond constructed by digging a hole and lining with a pond liner is much more cost effective than a concrete pond construction but cannot offer the same end results. This method is Ideal for keeping standard pond fish and Koi if the budget is tight.