Pond Filters: Biological vs Mechanical For Best Pond Filter

Filter pads from biological filter

Are you trying to find out how to keep your pond looking clean and clear? Do you want to make sure you’re making the right and best choice when it comes to pond filters so you can have a naturally balanced pond?

In this blog post, you will find out the differences between biological pond filters and mechanical pond filters. By the end of this post, you will know which of the two you need for your water feature.

Biological Filters vs Mechanical Filters

What They Filter

Biological filters help to remove suspended particles such as ammonia and nitrates from the water, making it cleaner and safer for all living things.

Mechanical filters, also called skimmers, are perfect for removing larger debris, such as leaves or twigs, from pool or pond water. 

How They Filter

Koi pond with biofalls pond filter

Biological filters use beneficial bacteria to break down organic pollutants in water. These filters are usually made with an air pump that pulls oxygen-rich water through the filter media, where it comes into contact with beneficial bacteria colonies.

Premier Ponds prefers using Biofall filters, which combines a biological filter and a waterfall.

Mechanical filters work by trapping large debris in some form of medium. This can be a skimmer basket, which collects leaves and debris much like a pool skimmer does. Some can also have sponges or other porous materials. As water passes through this medium, any particles larger than its pores get trapped inside.


You can’t really compare the effectiveness of these two types of filters because they both filter different things in water gardens.

People can argue that a mechanical filter is more effective at filtering ponds because it helps prevent organic matter from settling on the bottom and turning into muck.

Others can argue that biological filters are more important because it has a more direct impact on the quality of the water, which impacts everything else in the water garden.

Biological Filter Pros And Cons


  1. Effective Waste Removal: Biological filters are highly effective at removing harmful waste and toxins from the water. They work by creating an environment that’s hospitable to beneficial bacteria, which then break down organic waste and toxins. This helps to keep the water clean and clear, and it creates a healthier environment for aquatic life.
  2. Low-Maintenance: Once the filter is established, it can be left to do its job without much intervention. This makes it a convenient option for those who want a low-maintenance filtration system.
  3. Long-Lasting: Biological filters are built to last. They can provide years of effective filtration without needing to be replaced, as long as they are properly maintained.
  4. Natural Environment: Biological filters create a natural, healthy environment for aquatic life. They encourage the growth of beneficial bacteria, which helps to support the ecosystem in your pond. This can be especially beneficial if you have fish or other aquatic life in your pond.


  1. Slower Results: Biological filters can take longer to establish and start working than mechanical filters. This is because they rely on the growth of beneficial bacteria, which can take time to develop. In some cases, it may take several weeks or even months for a biological filter to become fully functional.
  2. Maintenance Requirements: Biological filters require some regular maintenance to keep them working effectively. This includes cleaning the filter media periodically to remove debris and other buildup that can interfere with filtration.
  3. Limited Flexibility: Biological filters are typically designed for specific types of ponds and aquatic environments. This means they may not be the best choice for every type of pond or aquatic ecosystem. If you have unique needs or requirements for your pond, a biological filter may not be the most flexible option.
  4. Limited Control: Because biological filters rely on the growth of beneficial bacteria, there is less control over the specific types of bacteria that are present in the filter. This can be a concern for pond owners who are trying to maintain a specific balance of bacteria in their pond ecosystem.
  5. Potential Clogging: Biological filters can be more prone to clogging than mechanical filters. This is because they rely on a media bed to support the growth of beneficial bacteria, and this media can become clogged with debris over time.

Mechanical Filter Pros And Cons

Cleaning a dirty skimmer


  1. Fast Results: Mechanical filters can quickly remove debris, such as leaves and other organic matter, from the water. This means you can see results almost immediately after installing a mechanical filter.
  2. Customizable Filtration: Mechanical filters offer more customization options than biological filters. You can choose from a variety of filter media types and sizes to meet the specific needs of your pond and aquatic ecosystem.
  3. Versatility: Mechanical filters are versatile and can be used in a variety of pond types and aquatic ecosystems. They are a good choice for both small and large ponds and can be used in conjunction with other filtration methods if needed.


  1. Higher Maintenance: While mechanical filters are generally easier to maintain than biological filters, they do require more frequent cleaning to ensure proper operation. This can be time-consuming and labor-intensive, especially for larger ponds.
  2. Reduced Oxygen Levels: Mechanical filters can reduce the oxygen levels in your pond. This is because they remove particles and debris from the water, which can lead to decreased oxygen levels. If your pond has a lot of fish or other aquatic life, this can be a concern.
  3. Limited Effectiveness: Mechanical filters may not be as effective at removing certain types of pollutants as biological filters. For example, they may not be as effective at removing nitrates and other nutrients from the water.

Other Factors To Consider

  1. Water Feature Size: The size of your water feature will determine the size of the filter you need. For larger features, a combination of both biological and mechanical filters may be necessary.
  2. Water Flow: Biological filters require a certain water flow rate to function effectively. Make sure your water pump is strong enough to provide adequate flow.
  3. Budget: The initial cost of a biological filter may be higher than a mechanical filter. However, biological filters require less maintenance and can be more cost-effective in the long run.
  4. Aquatic Life: If you have fish or other aquatic life in your water feature, a biological filter may be a better choice. These filters create a natural, healthy environment for your aquatic pets.

Which Is Better Overall?

Using both types of filters will give you maximum filtration performance since they work together to keep your pond clean and healthy.

By having both mechanical and biological filtration, you’ll get better results than if you were only using one type alone because each has its own strengths when it comes to cleaning your pond’s water.

Additionally, having both types will ensure that any debris or organic matter that isn’t caught by the mechanical filter will be broken down by beneficial bacteria in the biological filter before it has a chance to accumulate on the bottom or become suspended in the water column. This helps keep your pond looking crystal clear!  

Other Filters For Ponds

UV Filters

UV filters are a type of pond filtration system that uses ultraviolet light to kill bacteria, viruses, and other harmful microorganisms in the water. These filters work by passing water through a chamber that contains a UV lamp, which emits UV radiation that kills or sterilizes the microorganisms in the water. UV filters are easy to install and require minimal maintenance, making them a popular choice for pond owners. However, they may not be suitable for ponds with large amounts of debris, as this can reduce their effectiveness.

Aquatic Plants

Aquatic plants, such as water lilies and lotus, can act as natural filters for pond water. They absorb nutrients and organic matter from the water, which helps to reduce algae growth and improve water quality. In addition, they provide shade and shelter for fish and other aquatic life. However, too many plants can lead to oxygen depletion and poor water circulation, so it’s important to strike a balance between plant growth and water movement.


Fish can also play a role in maintaining water quality in garden ponds. They help to break down organic matter and consume algae and other microorganisms. However, too many fish can lead to overfeeding and excess waste, which can contribute to poor water quality. It’s important to carefully consider the type and number of fish you add to your pond and to provide adequate filtration and maintenance.

Pond Bog Filter

A pond bog filter, also known as a bog garden or wetland filter, is a type of biological filter that uses plants to filter and purify pond water. It consists of a planted bed or shallow pool of water that allows water to slowly flow through layers of gravel and sand, where beneficial bacteria and plant roots work together to remove nutrients, debris, and pollutants from the water.

Use Premier Ponds To Keep Your Filters Working For A Cleaner Pond

No matter the type of filter, or filters, you have in your outdoor water feature, it’s important that you keep it maintained and clean. Then you can enjoy your beautiful feature even more!

Premier Ponds is here to help you with keeping up with your biological or mechanical filter needs. We have an experienced staff who can answer all of your questions and provide amazing services on your behalf.

Reach out to us by filling out our contact form today or calling us directly. You’ll be glad that you made the decision to use Premier Ponds for all of your water feature maintenance needs.


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