Biological filtration is a critical process in aquaponics and other aquatic systems where beneficial bacteria play a key role in converting harmful substances into less toxic forms. In the context of aquaponics, biological filtration is primarily involved in the conversion of ammonia, a waste product produced by fish, into nitrites and then into nitrates. This process is known as the nitrogen cycle.
Here’s how biological filtration works in aquaponics:
- Ammonia Production: Fish release ammonia into the water through their gills and excrement. Ammonia is toxic to fish, and if its levels become too high, it can be harmful or even fatal.
- Nitrosomonas Bacteria (Nitrification – Part 1): Ammonia is first broken down by bacteria of the genus Nitrosomonas. These bacteria oxidize ammonia into nitrites (NO₂⁻). Nitrites are still harmful to fish, but they are less toxic than ammonia.
- Nitrobacter Bacteria (Nitrification – Part 2): Nitrites are then further oxidized by another group of bacteria, typically of the genus Nitrobacter. These bacteria convert nitrites into nitrates (NO₃⁻). Nitrates are much less harmful to fish compared to ammonia and nitrites.
- Plant Uptake: Nitrates, which are plant-available forms of nitrogen, are then absorbed by the plants through their root systems. This nutrient-rich water is beneficial for plant growth.
- Water Quality Improvement: As the plants take up the nitrates, the water is effectively filtered and purified. This creates a symbiotic relationship where the fish provide waste that is converted into nutrients for the plants, and the plants, in turn, help to clean the water for the fish.
The overall process of nitrification involves the establishment and maintenance of a robust bacterial population in the aquaponics system. It is important to allow time for these beneficial bacteria to colonize the system, typically during the initial cycling phase of the aquaponics setup.
Proper management of biological filtration is essential for maintaining a balanced and healthy aquaponics system. Regular monitoring of water parameters, including ammonia, nitrite, nitrate levels, and pH, helps ensure that the nitrogen cycle is functioning effectively, providing optimal conditions for both the fish and plants in the system.