Pond Filters Guide: Best Pond Filter & Types of Filtration


A good pond filter is key to having a successful pond. Filtration keeps the pond water clear, oxygenated, and healthy for the fish living in the pond. Today, there are many different types of pond filters with various features. One popular feature is UV light filtration. UV light is used to will kill bacteria and algae. This can be useful if your pond is struggling with water clarity. In addition to the different types of filters, it is important to understand what size pond filter you need for your pond. This article will help you choose the best pond filter that is most suited for your needs.

Why Do You Need a Pond Filter System?

A pond filter helps keep the pond ecosystem healthy and thriving. It helps create an environment that is suitable for beneficial bacteria to thrive, which helps accelerate the nitrogen cycle. Ultimately, this creates an environment that is habitable for fish and other aquatic organisms.

While many people assume that the purpose of the pond filter is to collect the debris and small particles floating in the water, this is only secondary function.

Pond Filtration

The primary function of a pond filter is to keep the water oxygenated, which helps create a suitable environment for beneficial bacteria. Without the beneficial bacteria, the waste that the fish produce will accumulate as ammonia in the pond very quickly. This is the reason why a stagnant pond without a proper filtration system will not be able to support very many fish.

What Size Filter Should You Use for Your Pond?

When choosing the right filter size for your pond, choose a filtration system that has sufficient flow rate. Filtration flow rate is commonly measured in gallons per hour (gph). The rule of thumb is to install a filter with a gph rating of 1.5 times the number of gallons in your pond. For example, if you have a 100 gallon pond, get a filter that is rated for 150 gph.

The flow rate of your filtration system will influence the oxygen level in your pond, which is very important. Therefore, if you are stuck choosing between two filters of different sizes, go with the larger one. A little extra water flow will not hurt your pond, but a stagnant pond will not support life.

Types of Filtration in a Pond Filter

There are different types of filtration, and different manufacturers design pond filters with different components. Therefore, it is important to understand the function and purpose of each filtration type, in order to choose the one that best suits you. Some of the most common types of filtration in a pond filter are, mechanical filtration, biological filtration, and UV filtration.

Mechanical Filtration

Mechanical filtration within a pond filter collects small and large pieces of debris in the water. The water pump moves water through the filter media, which catches debris such as leaves and uneaten food particles. Filter media may consist of multiple different material such as brushes and sponges. The largest debris may be collected by a pre-filter before it goes through the filter media as well. Removing the debris and sediments in the pond water is important because it keeps the water visibly cleaner, and it prevents the debris from clogging the biological filtration. Mechanical filtration is a basic type of filtration that it is a component that is found in almost every pond filter, and it helps improve water quality immensely.

Biological Filtration

Biological filtration within a pond filter houses the beneficial bacteria, which processes the organic waste material. Uneaten food, fish waste, and other nutrients in the water turns into ammonia and nitrites. Accumulation of ammonia and nitrites is dangerous to fish, and it will kill them at high concentrations. The beneficial bacteria in the biological filtration will help process the ammonia and nitrites into nitrates, which are less harmful to the fish. This is part of the nitrogen cycle. Biological filtration is especially important if your pond is well-stocked with fish. Keep in mind that a biological filter requires time to get established. This is because there are no beneficial bacteria in the filter when the filter is installed initially. The biological filter simply provides the necessary surface area for the beneficial bacteria to grow on. Over a period of time, the beneficial bacteria will slowly establish itself on the biological filter media. Therefore, if you are installing a new filtration system, it is best to allow the pond to cycle before adding lots of fish. Popular media for biological filtration include plastic bio-balls and ceramic rings. Biological filtration is one of the most important functions of a pond filter.

UV Filtration

UV pond filtration, or UV sterilization, in kills off algae and other free-floating microorganisms. The powerful UV light will kill the algae, so if your pond is struggling with green water, this may help. However, keep in mind that types of algae that are not free-floating, such as string algae, will not be affected. In addition, microorganisms that are killed by the UV light may include both good and bad bacteria. Therefore, it is important to consider the advantages and disadvantages when using a UV filter. Make sure the biological filtration system is well established before using a UV filter. In some cases, it may be better to turn on the UV filter only when necessary.

What is the Best Pond Filter?

The best pond filter currently on the market is the SUN Grech CPF-2500. Considering the price and feature it provides, this is certainly the best pond filter for most people. It features an efficient design that will removal of dissolved and solid waste. Maintenance is easy since it does not require you to open the entire filter every time.

Since this is a pressure filter, it allows higher flow rate compared to traditional gravity filters. Another advantage of the pressure filter is that it can be dug in at the edge of the pond, and position the outlet at a higher position than the pond. This pond filter has a flow rate of approximately 1600 gallons per hour (GPH). Therefore, this unit will support a pond of approximately 900 gallon in size.

If you have a koi in your pond, keep in mind that koi fish produce lots of waste. This is especially true if you have large koi, or a large number of koi. A powerful and reliable pond filter such as this unit will be crucial for the health of the fish and the entire pond.

Considering the fact that it features a UV light at this price point, the SUN Grech CPF-2500 is certainly the one of the best pond filter currently available.

Fish Laboratory

With decades of collective fishkeeping experience, we are happy to share the knowledge that we've picked up along the way. Our goal at Fish Laboratory Aquatics is to keep publishing accurate content to help fishkeepers keep their fish healthy.

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