Biofiltration in Aquaponics Explained

October 07, 2021

Don’t be scared off by the name. It’s not as complex to set up as it might sound. Biofiltration in aquaponics is the crucial mechanism that allows the cycle of aquaponics to take place. Your fish could get sick and your plants will be deprived of nitrogen without adequate biofiltration in an aquaponics system. But how does this happen, you ask? Well, let’s explain a bit more about the ins and outs of biofiltration in aquaponics.

What is biofiltration?

As you should already know, the nitrogen cycle is the magic cycle that makes aquaponics all possible. If you haven’t learnt about the chemistry behind aquaponics, then please take a look at our blog posts linked as they cover it all in detail.

Two important bacteria carry out the nitrogen cycle. Additionally, these bacteria need a home to live in our aquaponics system to carry out these chemical equations. Therefore, we create a biofilter. Biofiltration is merely the process that these bacteria carry out. In other words, the conversion of the fish waste into nitrates for the plants to absorb.

Why is biofiltration important?

Without biofiltration, the fish waste will accumulate in your aquaponics system and therefore become toxic to your fish. And your plants will also be deprived of their nitrogen intake. It’s therefore, important to have a biofilter in your system design because you need to ensure that you have enough surface area for your bacteria colonies to grow.

Different Methods of Biofiltration

Flood and Drain Grow beds

This is one of the reasons we love having a media bed in our aquaponics system setup. A media bed acts as a built-in biofilter. This is because the media provides a large surface area for the bacteria to colonize. To ensure you have sufficient surface area to support your tank, make sure you have: 1sqm of media bed per 1000l tank. However, we still recommend using a Metala filtered biofilter even if you have media beds in your system.

Bio Balls

These balls provide the perfect environment and surface area for the bacteria to colonize. 16 balls per litre is an adequate amount for filtration. Additionally, we would recommend using the black balls to prevent any algal growth.

Bird Netting

This might look like the easiest and most inexpensive method. But don’t be fooled. This method requires a lot of elbow grease. Literally! So prepare to get your hands dirty if you decide to use bird netting as you will be cleaning the netting quite regularly.

Matala Filter Media

Our number one choice when it comes to Biofiltration! Just like the mechanical filter, we like to build a biofilter that is separate from the system. The water will flow through here directly after flowing through the mechanical filter. The Matala mats create an extremely high surface area for bacterial colonization. Moreover, we find that a Matala mat biofilter is the most cost-effective and compact option for biofiltration. 30cm x 30cm x 4cm per 1000 litres is usually adequate.

Caring for your biofilter

The single most critical element of biofiltration is making sure you have plenty of oxygen available. Because, without oxygen, the bacteria cannot carry out the chemical equations that convert the fish waste into nitrates. A biofilter also needs to be cleaned regularly. Don’t worry, cleaning it won’t wash away the beautiful bacterial colonies that have inhabited your biofilter. Don’t use soap! Just a good rinse and scrub. This cleans out that excess fish waste that wasn’t filtered out during mechanical filtration. We like to keep things extra clean in our aquaponics system to ensure smooth sailing cycles all round.

Well, now you have all the knowledge and understanding needed when working with biofiltration in aquaponics. Biofiltration is about creating the desired environment for your bacteria to colonize themselves. If you have any design questions about building your own biofilter please don’t hesitate to book a 15 min consultation with us.