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Benefits of UV Filtration in your Pond

Keeping your pond free from algae and harmful bacteria can be difficult, but making sure your pond has a UV bulb is an important step in keeping your pond healthy.

21 September 2021

Maintaining healthy water in your pond can be difficult; particularly when algae blooms can be so prolific on sunny days or when the weather is warmer. The easiest way to keep a pond clean is to install a UV Clarifier into your pond, either through your filter or as a standalone product.

We have created a helpful, informative guide below on how a UV bulb works and why its so crucial to have one in your pond.

What does UV filtration do?

In short, the UV radiation helps to disinfect the water and it helps to remove algae particles in the water, working in conjunction with a suitable filter system. In keeping the pond free from these problems, your pond will become established much sooner than normal and the chemicals in the water will become balanced quicker, saving both time and money.

UV clarifiers are not harmful to your fish or the beneficial bacteria in the pond. The beneficial bacteria in your pond will still reside on gravel, stones, biological media in your filter or other areas in the pond; they remain unaffected by the UV bulb. By controlling the development of algae and harmful bacteria in your pond, the UV bulb can prevent the spread of microorganisms transferring from one fish to another.

They are a useful tool to have in keeping your pond clean and healthy, both for any wildlife or fish in the pond, but also for the aesthetic beauty of the pond.

How does a UV clarifier work?

The UV works by sterilizing the water; as the water passes the UV bulb, algae particles are flocculated (or bound together) into clumps; these clumps are then caught in the mechanical filtration of your filter (foams, brushes, cartridges etc). This prevents harmful bacteria from developing due to a build up of algae and keeps your pond clear.

Our filters come with UV bulbs included as part of the filter (unless stated otherwise, like the Hozelock Ecocel units, Solar Filters or the Fish Mate Powerclenz Bio filters as these do not include any UV filtration). If you feel like you need to increase the levels of UV filtration in your system, you can purchase an external UV clarifier; this is an external UV bulb that is situated outside of the filter and works in the same way. So, if you have a 25w UV in your filter, you can supplement this with a 36w UV located outside of the filter.

What Size UV Steriliser Do I Need?

In most cases, when you purchase a filter containing a UV bulb, the UV bulb will match the pond size that the filter is suitable for. But in some situations, this may not be enough, particularly if you have an overstocked pond or a Koi Pond.

For a wildlife pond, we recommend 1w per 1000 litres; please note, a wildlife pond does not require a UV bulb as standard.

For a Goldfish Pond, we recommend 2w per 1000 litres.

For a Koi Pond, we recommend 4w per 1000 litres.

You will need to replace the UV bulb in your filter or clarifier every 6 months of continuous use. You can view our complete list of UV Bulbs here.

UV filtration provides a safe and easy way to maintain healthy water, which in turn keeps your fish and pond ecosystem healthy. If you have any queries, please email us on

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