A bio filter is one of the most important pieces of equipment any aquaponics system will need. Since the aquaponics system is a balance of plants, fish and beneficial bacteria, the bio filter will help maintain the balance and make your life much easier.
So what is a bio filter?
A bio filter is just a place where the good bacteria colonize and multiply. When fish excrete waste into the water, there is a buildup of ammonia in the water and bacteria is necessary to break down the ammonia into nitrates which are beneficial. This process is known as the nitrogen cycle or nitrification.
Since your aquaponics system will require a healthy amount of nitrates in the water as nutrients for the plants, a bio filter is essential. It will usually take about 3 to 6 months for there to be sufficient bacteria in the system.
Depending on the type of aquaponics system you go with, the presence of a bio filter may or may not be necessary. In the raft system, a bio-filter is not necessary since the plants are submerged in the water all the time. The bacteria will build up slowly over time on the rafts, walls of the container and most of the surfaces that are in constant contact with the water.
However, since the flood and drain method is more effective for almost all aquaponics systems, you will be well-advised to go with this method rather than the raft system. However, with this system, a separate bio filter will be essential.
You will need a container or trough that is well aerated. Usually, an air pump is used to aerate the water. The waste water that is pumped on to the media bed will drain back to this container and for 12 hours the water will have time for the bacteria to multiply. The water is pumped back on to the media bed again 12 hours later and the cycle repeats.
If you’re still unclear about what a bio filter is, just think about the under gravel filter in a fish tank you keep at home. The wastes are trapped beneath it and slowly broken down by the bacteria which in turn multiply. Most fish are perfectly happy living in their own waste water for as long as possible provided the ammonia is broken down. If you wish to have a successful aquaponics system, this is the most crucial aspect of it.
Many aquaponics enthusiasts speed up the process by adding a bacteria mix that they purchase from an aquarium supplier. They add this into the water once the fish are introduced into the system. This is often costly and not really necessary if you are willing to wait. Furthermore, there is no guarantee that the mix will create good bacteria.
If you’re wondering whether you have enough good bacteria in your tank, there is a pretty straightforward way to find out. Just test and measure the levels of ammonia, nitrates and nitrites in the water. You may get the test kits from any reliable aquarium supplier.
To summarize, you must have good bacteria present in the water and they need a place to grow and multiply. Asses your system and decide if you need a bio filter and where it should be. Then set it up, give it time and the bacteria will grow. It’s that simple.