What Is Aquaponics Biofilter? - Go Green Aquaponics

What Is Aquaponics Biofilter?

Many aquaponics beginners are often confused by the need for filtration in their aquaponics system. Do I need to add a biofilter? It is one of the frequently asked questions in aquaponics. To answer the question, we wrote this article to discuss biofilter, what it is, and do you need to have one in your aquaponics system.

The idea behind aquaponics is that it is possible to imitate nature to create a perfect growing environment for the fish and plants to grow. Aquaponics is a recirculating method of farming that combines aquaculture and hydroponics, leading to the raising of fish and growing plants together in a symbiotic environment with beneficial bacteria. It converts wastes produced by the fish into nitrates, which become plant food, and in return, the plant roots filter and clean the water for the fish. A biofilter helps this process to ensure that nothing goes to wastes.

What Is A Biofilter?

A biofilter is a place for the bacteria to colonize. It provides large surface areas, pH, dissolved oxygen levels, and proper temperature.

Biofilters are quite simple to set up, and they consist of a tank connected to the air pump and some substrates that provide as much as possible a big surface area for the nitrifying bacteria to grow. The more surface area for the bacteria to develop, the better because it means a more efficient nitrification process.

Biofilters In Aquaponics

What is Biofiltration?

Biofiltration is the process of converting ammonia and nitrite into nitrates by the beneficial bacteria. Ammonia and nitrites are toxic to aquaponics, even at low concentrations. However, plants need the nitrates to grow, so a biofilter needs to be installed to house most living bacteria. The water movement within a biofilter will break down the very fine solids not captured by the clarifier, which prevents a waste build up on the plant roots in the NFT aquaponics system. Good biofiltration is also essential for the chemical stability of your aquaponics system. Separate biofilters are unnecessary for the media-based aquaponics system because the grow beds themselves are perfect biofilters.

Why Do you Need A Biofilter

In aquaponics, if the surface area in your grow media is not enough for the bacteria to colonize, you need to add more surface area. This is why you need to have a biofilter. The biofilter will form an important part of your system by ensuring that plants have enough nutrients to grow healthy while cleaning the water for the fish to live. 

Your whole aquaponics system is a biofilter. However, if you are using the DWC, Vertical, and NFT aquaponics system to grow your plants, you will need a biofilter. In these types of aquaponics systems, you can't rely on the natural process of bacterial conversion because of a lack of adequate surface area. A media-based or raft aquaponics system does not usually need a separate biofilter because the raft, growing media (expanded clays, gravel, or lava rock), tank walls, and other surface areas provide enough area for the bacteria to colonize.

Benefits Of Using Biofilter In Aquaponics

1. It provides more surface area for the beneficial bacteria to live and helps convert ammonia and nitrites into nitrates.

2. Biofilter assists in aeration and nitrification processes in the NFT, DWC, and Vertical aquaponics systems.

3. Aid in the chemical stability of your aquaponics system.

4. Very inexpensive and easy to build.

5. Very easy to use and require very little maintenance.

Important Factors to Consider before Using Biofilter

Before you decide to use biofilter in your aquaponics system, you must be aware of these considerations.

  • Remove The Solids First

Biofilters are not for large solid fish wastes. Solids must be screened because this will possibly block the pipes. Once these solids accumulate in your biofilter, this will create areas known as aerobic zones that will attract bacteria and reduce your biofilter's surface area. This will reduce your biofilter's efficiency, which will result in a high ammonia level, which is not suitable for fish and plants. That is why it is important that you add a standard filter that will remove the solid.

  • Bacteria Need Air

In an aquaponics system, the bacteria are exposed to the air. Adding a biofilter to your aquaponics system will contain the bacteria in the filter. So you have to make sure that your filter has enough air supply to ensure that the bacteria are not deprived of air.

  • Fish Density

If you are running a low fish density, then you don't need a biofilter. Low quantities of fish will not produce enough waste to justify the use of a biofilter. The plant's roots will provide enough surface area for the bacteria to convert ammonia into nitrates.


How Do Biofilters in Aquaponics Work?

The biofilter is the extension of the surface area of your aquaponics system. It is an essential part of your aquaponics system because it ensures that your plants can access the nitrates that they need to grow while cleaning the water for the fish. The bacteria will attach to the surface of your biofilter media. Once they are established, they do their job and help convert ammonia and nitrites into nitrates. 

Biofiltration in aquaponics happens in three main steps. This process is for typical aquaponics set up. The process or steps may vary depending on your biofilter design.

1. The air pump pumps the water out of the fish tank and into the biofilter.

2. Inside the biofilter, the water goes through the nitrification process. The beneficial bacteria help convert ammonia and nitrites into nitrates.

3. The water full of nutrients flows out of the biofilter and into the plants, where the plant roots absorb the nutrients while cleaning the water before it goes back into the fish tank.

Different Biofilter

There are several aquaponics biofilters that you can use in your aquaponics system; these are:

  • Moving Bed Filter

This biofilter is used in a floating raft system where there is not much surface area for the bacteria. 

  • Static Filter

These are tray-like filters that can be slid into a separate container next to the fish tank before the plants. These provide a large area for the bacteria to collect on. This filter needs to be positioned after the solid filter before it reaches the plants, allowing the water to be filtered before it reaches the plants.

  • Drip Filter

This filter allows water to drop in from the top. The water passes through the filter box, full of gravel, oyster shells, or another similar bio medium with lots of surface area. This biofilter also needs to be positioned where the water is filtered before it gets to the plants. As the water moves through the filter, the ammonia is converted to nitrates before it is pumped back to the plants.


Good biofiltration is essential for the chemical stability of your aquaponics system. That is why it is important to understand the role of a biofilter in aquaponics to know if your system needs a biofilter. If you have any comments, feel free to leave them below.


3 Responses



July 27, 2021


Wm David Wilhelm

Wm David Wilhelm

July 27, 2021

In addition to a Bio media filters for fish outlets, I am considering using a Bio media pre-filter for all returns from plant media beds for fine particulate accumulation and additional mineralization with airlift and higher O2 levels for fish. If it all works, as designed and will reduce the addition of nutrient top off and JAW (just add water) is the goal and best wishes to all. Hint, hint, Catfish for any Crayfish that get loose from the system floating mats, vertical racks primers for faster nutrient uptake crops and cleaner clearer water. Circularize your plant media beds for less stagnation and anaerobic activity, by spiralizing the water flow.

Daniel Schneekloth

Daniel Schneekloth

July 27, 2021

I know my question is not gonna be a black or white answer as it probably depends on water quality and other factors too. But is there a volume of water flow rate per amount of surface area of your bio filter? Just using random numbers as example. Say 50 gallons a minute for 5000 square feet of surface area?

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