UV pond filters are actually UV water clarifiers, not filters. Their job is to tackle algae and bacteria within the water to help keep it clean and safe for pond life. The filtering part is usually performed by a mechanical or biological filter, often within the same device.

UV light is known to address bacteria and algae, which is why they are so important for ponds.

In our experience, almost every type of pond needs some kind of UV pond filter to keep algae at bay. They aren’t the only way to remove algae but they are the easiest, lowest maintenance and least intrusive way.

Some plants filter water and some fish eat algae but these work better in conjunction with a UV pond filter rather than instead of one.

The size of the UV pond filter you need for your pond depends on its size. As a general guide, you want 10w of UV filtering per 4500 litres of water for clarification. You’ll need up to 30w per 4500 litres if you want to sterilise the water or have a particularly robust form of algae in your pond.

UV pond filters will begin working right away and the time it takes to clean a pond depends on the size of that pond and how dirty it is. You’ll begin seeing positive differences within 24-48 hours and you can expect the water in an average pond to be clear, or almost clear within 10-14 days.

We recommend changing the lamp in your UV pond filter around once a year. UV pond filters use UV lamps to provide the clarification effect.

These are user-changeable parts and can be easily replaced as required. Lamps may last longer than 12 months, but unless you check, you won’t know whether it’s working or not until your pond begins turning green.

We suggest checking the lamp as part of your regular pond maintenance routine.

You cannot have too much UV filtering. UV pond filters remove algae and bacteria, nothing else. It isn’t like adding too much chemical cleaner to the water or something more invasive. UV light cleans whatever it finds and will not impact water Ph, fish or other pond life.

We do recommend using the right wattage for the pond size, but that’s more about running costs than anything else.