How To Choose A Pond Filter

All ponds need a filtration system to keep the water clean, clear and healthy. Stocking levels of fish are much higher in a garden pond than in the wild and, without a filter, impurities accumulate to create a toxic environment.

Mechanical and biological filters, together with UV clarifiers, will cleanse the water to create the best possible environment to encourage a thriving population of fish and plant life.

Mechanical Filters

Dirty water flows through the filter, foam or other media that captures debris. Filtered clean water then returns to the pond.

Biological Filters

This process involves a filter medium that contains beneficial bacteria that cleanse the water.

UV clarifiers

These are included in many filtration kits and available separately with the UV helping to eradicate 'green water' by eliminating algae.

For ponds up to 10,000 litres, box filters are the best choice, they may contain a clarifier and can be biological or alternatively mecanical. If you prefer, some boxes can be hidden underground or you might choose a filter that can be immersed. 

Pressurised units allow you the option of powering a waterfall or fountain and more expensive filters feature advanced technology, can handle larger volumes of water or offer functions that are labour saving and can significantly reduce running costs. These include self-cleaning systems and power saving devices that enable the UV filter to switch off when not required.

Filter Capacity

When choosing a filter, consider what is most appropriate for your particular requirements. Follow the manufacturer’s recommendations on the filter’s capacity and the volume of water it can process. Remember that water should be circulated at least once every two hours i.e. a 2000 litre pond will need a filter that generates a flow of 1000 litres per hour.

Don’t forget that if you have fish, take into account how many and how large they are, as this can dramatically affect the specification that is required, as can factors such as whether you want the clean water to be pumped to fountains or other ornaments.

Also think about practicalities such as the ease of maintenance, perhaps a self-cleaning system is preferable. Running costs must also be considered, both in terms of the amount of power required and the durability and longevity of the product parts.

There is no doubt the range of pond filters on the market is daunting and can be confusing. Basic facts such as the volume of water, number of fish etc are vital components in making a decision, the rest is probably personal choice, preferably reinforced by the advice of a specialist retailer.