Blog & Latest News from the team at Water Garden Ltd - What Is the Best Pond Filter for Koi?

Given their large size and healthy appetites, it is essential to install an effective filtration system in your Koi pond if you want to prevent the build up of nitrogenous waste and maintain water clarity. Failure to deal with nitrogenous waste and particulate matter could have a negative impact on the health of your fish and in the worst case scenario, result in a total loss of stock. This is especially the case as far as metabolic (nitrogenous) waste products are concerned: ammonia, nitrites and, to a lesser degree, nitrates.

Choosing the Best Filtration Equipment for Your Pond.

The best type of filtration for your Koi pond will depend largely on its size and your stocking levels. There are a number of different types of filters currently available in the UK, the 3 most popular of which are listed below.

Filtral Pond Filters

In Pond Filters – Popular with some pond owners, owing to the fact they are submerged out of sight and come as all-in-one units, with both a pump and filter in one compartment.  They are not however a good choice for larger ponds or those with more than a handful of fish. If you install this type of filter in a big pond that is heavily stocked, it is likely to be overwhelmed by the level of waste with which it has to deal with. Furthermore, because they are installed at the bottom of the pond, cleaning the filter and pump impeller mechanism is not such a simple task as cleaning an externally mounted filter.

Gravity Flow Through Filter

Gravity Flow-through Filters – Traditionally the most popular pond filter type, gravity flow through filtration units consist of a box filter with multiple chambers or sections, each of which contains a certain type of filtration media. The fact they can perform both biological and mechanical filtration and are easy to clean because they are situated out of the water, has helped to make these filters a common site in gardens across the country. However, the nature of box filters means that the filter outlet must be above the water level of the ponds in which they are used. This lack of flexibility as far as positioning is concerned has led to other, more flexible, types of filter gaining in popularity in recent years.


External Pressure Filter – It is fair to say that external pressurised filters are the most popular choice nowadays, thanks mainly to their efficiency, ease of maintenance, and flexibility with regard to positioning. Water is driven into these filters by a pump, where it then passes through various types of filtration media before returning to the pond. The one drawback with many external pressure filters is that they are quite small and therefore do not have a large volume of filter media. This means they need to be cleaned more regularly than a larger gravity flow-through filter.

If you want to keep the water in your Koi pond in excellent condition, please feel free to call for expert advice and more information on all pond filtration options currently available.

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