All ponds require filtration. Whether a pond is large or small, the fish in it cannot survive if you do not install this key piece of equipment. Even if a fish does survive without the use of a filter, they will still suffer from the toxins in the water. In order for a filter to work, it must be able to manage a large volume of water per hour. It must also feature electrical connections that are waterproof, and its container must be able to withstand the outside elements.
Therefore, a pond filter must be able to filter through all the water in a pond at least once per hour. Submerged water pumps are used with some filtration systems as well. This method involves sending the water, via the pump, to the filter, after which it is then released back into the pond. Regardless of the exact method used, a filter typically sits above the waterline to permit the filtered water to drop back into the pond.
A Highly Recommended Product
Filters come in a variety of styles, including biological filters and internal and external units. If you have both fish and plants in your backyard pond, you should select a UV pond filter or a biological filtration system. A biological filter removes waste and debris as well as organic compounds and chemicals. If the filter uses UV light, it will get rid of algae cells as they flow through the water as well. Filters that provide multi-stage filtration and a UV light are highly recommended by filtration suppliers.
Filter maintenance is important, since pond filters are vital to cleaning pond water of debris and toxins. When the filter is well-maintained, the unit will run at the highest efficiency to ensure that the water is pure and pristine. When selecting a filter too, always consider the wattage rating, as a higher amount of wattage will increase your energy costs.
In-pond Filters
If you need a versatile and compact unit, you may want to consider an in-pond filter for your water garden. Some of these units come with a UV clarifier to remove algae cells before they accumulate. If you have a fish-free pond that is 3000 litres in size, then this is an ideal filter to use. The biomechanical system eradicates contaminants, debris, and waste. This type of unit may also feature various water-fountain effects.
Pressurised Pond Filters
Pressurised pond filters provide another alternative for pond cleaning. These filters can be installed above or below the ground. Most of the filters blend in well with your garden and do not detract from the look of an outdoor space.
As water passes through the filter media, the sludge is forced out, leaving a clean water supply. Many of these filters feature multi-stage filtration, which continues to clean the water as it is passing through the system. The device uses both biological and mechanical filtration.
Pond Kits
You can save money if you choose a pump and filter kit. As indicated, a pump and filter work in conjunction to ensure that water is cleaned to the highest standard. Many of these kits are used in fish-free ponds that are approximately 5,000 litres in size. Kits are recommended for ponds containing fish that are about 3,000 litres in size. Choose this product if you need to clean the water in an average-sized pond.
Daryl Green 
Barbara Ratliff