Pond filters work in a couple of different ways. Mechanical filters physically remove debris from the pond while filtering water, UV pond filters use ultraviolet light perhaps alongside mechanical filters to clean the water. Bio pond filters use biological filtration to filter and clean the water.

Some filters use a combination of these three systems to provide clean, fresh water for your fish.

We recommend using a filter that can filter 150% of your pond's water volume. That way, the filter is never put under pressure and should offer the longest, most reliable operating life.

For example, if your pond is 2m x 3m and 1.5m deep, the volume is 9m3 or 9000 liters. In this situation we would recommend a pond filter capable of handling 14,000 liters.

You can over filter a pond but it shouldn’t harm the fish or plants within the pond. The main downside of over filtering is energy wastage and using a more expensive pond filter than you need to.

Fish can survive in unfiltered water as long as there is sufficient plant life to provide oxygen and help clean the water. There are additives, such as Aquaplancton that can help manage the bacteria in the water but filtration is the cheapest, simplest way to keep fish healthy and ponds clean.

Pond filters should require minimal maintenance. Depending on the type of filter you use, maintenance will just include checking inlets and outlets for blockages, clearing out any sludge from the filter and cleaning the filter itself.

This can be part of annual maintenance or be performed more often. Much depends on the size of the pond, the stock and any plant life you have in the pond.

You should keep your pond filter running 24/7. Whether that’s a mechanical filter, pond gravity filter, UV pond filter or something else, you should install it and leave it running all day every day.

As long as you buy the right type and size of pond filter for your situation, there is no danger to the fish or other life in the pond if you leave the filter running 24 hours a day.