The first thing that comes to mind when people think of an aquaponics system is the fish and plants, as we often define aquaponics as a combination of raising fish and growing plants. However, bacteria is an equally important component of your aquaponics system. To run a successful aquaponics system, it is vital to have all three components; fish, plants, and bacteria.
The Role of Bacteria in Aquaponics
An aquaponics system requires beneficial bacteria for the fish and plants to thrive. Bacteria break down the fish waste, keep the water clean for the fish, and turn the fish waste into a usable form of nutrients for the plants. Plants' roots absorb the nutrients from the water, which then helps to clean the water for the fish to live. Before the plants can absorb the nutrients, the nutrients must be converted into nitrates.
Bacteria usually live on the bottom of the fish tank, and the grow media in the grow beds. Fish waste and excess food settle at the bottom of the tank, and the bacteria work on breaking down this waste.
The Nitrification Process in Aquaponics
The nitrifying bacteria plays an essential role in an aquaponics system. The nitrifying bacteria convert fish waste, which enters the system as ammonia, into nitrates that fertilize the plants.
The nitrification in aquaponics is a two-step process and involves two nitrifying bacteria:
- Converting Ammonia Into Nitrites- The waste produced by the fish, which is full of ammonia, is converted by Nitrosomonas into nitrites.
- Converting nitrites into nitrate- This is done by Nitrobacter. Nitrobacter bacteria feed off nitrites. The nitrates are converted into nitrates once the nitrites are consumed by Nitrobacter. Plants grow rapidly when they absorb nitrates. Excessive nitrites can kill the fish. To keep the fish and the plants healthy, nitrites must be converted into nitrates.
Nitrifying bacteria are slow to reproduce and establish colonies; It may take days, weeks, or even months. There are five key parameters to support nitrifying bacteria. Nitrifying bacteria requires a dark location, good water quality, and adequate food and oxygen to colonize.
Parameters for the Bacteria to Colonize
If these parameters are observed, it will be safe to assume that the bacteria are present and functioning well.
1. High Surface Area
Bio-filtration with a high specific surface area is essential to develop extensive colonies of nitrifying bacteria. Many materials can be used in aquaponics, either as growing media or for biofiltration. Volcanic gravel, expanded clay pebbles, commercial plastic bio-filter balls, and plant roots act as a surface area for the bacteria to live on. The smaller and more porous the particles are, the greater the surface available for bacteria to colonize, which will cause more efficient biofiltration.
2. Water pH
Nitrifying bacteria function correctly when the pH levels are between 6 and 8.5. The ideal pH in aquaponics is usually 6-7, a compromise between all the organisms in the system.
3. Water Temperature
The ideal temperature range for the bacteria is 63 °F - 93 °F. This range encourages growth and productivity for bacteria. The bacteria's productivity will decrease if the water temperaturedrops below this range.
4. Dissolved Oxygen
Nitrifying bacteria need adequate dissolved oxygen in the water to grow healthy and maintain productivity. The optimum level of dissolved oxygen is 4 - 8 ppm. Nitrification does not happen if the dissolved oxygen concentration drops below 7.0 ppm. You can ensure adequate bio-filtration and dissolved oxygen by adding aeration using air stones or through flood-and-drain cycles in media beds.
5. UV Light
Nitrifying bacteria are photosensitive until they are fully established, and sunlight can cause harm to the bio-filter. Media beds protect the bacteria from sunlight, but if you use a biofilter, keep it shaded from direct sunlight.
Unwanted Bacteria
Nitrifying and mineralizing bacteria are essential and valuable to aquaponics, but some bacteria are harmful to aquaponic systems. These are:
1. Sulphate- Reducing Bacteria
These bacteria are often found in anaerobic conditions and have an odor of rotten eggs. These bacteria have a grey-black color and grow only in anoxic conditions. It is essential to provide adequate aeration and to increase mechanical filtration to prevent the accumulation of these bacteria.
2. De-Nitrifying Bacteria
These bacteria also thrive in anaerobic conditions and are responsible for denitrification. They convert nitrites back into atmospheric nitrogen that is unavailable to plants. In aquaponics systems, these bacteria can decrease efficiency by removing nitrogen fertilizer.
3. Pathogenic Bacteria
These bacteria can cause diseases in plants, fish, and humans. It is important to have good gardening practices to minimize the risks of diseases in an aquaponic system. You can prevent pathogens from entering the system by keeping household pets, animals, and other fish away from your system. Placing your aquaponics system in an enclosed greenhouse will also help to prevent pathogenic bacteria from entering your system.
System Cycling and Creating a Biofilter Colony
System cycling refers to establishing a healthy bacteria colony when starting your new aquaponics system. Cycling takes place once a new aquaponics system is built and usually takes 3-5 weeks. The process involves introducing an ammonia source (usually fish) into a new aquaponic system, feeding the new bacterial colony, and creating a biofilter. The progress of your cycling is measured by monitoring nitrogen levels.
Without bacteria, the nitrogen cycle will not occur. The nitrogen cycle transforms ammonia from fish waste into nutrient-rich fertilizer for plants. The nitrogen cycle will only take place when the nitrifying bacteria is present. For cycling to occur, ammonia must be added to the system. This ammonia can be added using the fish or water from another aquaponics system where the bacteria colony is already established. As more ammonia is added, more bacteria are produced, which makes the system work efficiently. Once ammonia-converting bacteria is established, it has nitrites, which allow the bacteria to use nitrites and produce nitrates. A system is fully cycled once ammonia or nitrites are measurable during testing.
Fishless Cycling
This process is often used in new aquaponics systems or tanks because it can be done without concern about the fish's safety. To begin fishless cycling, you must introduce ammonia without fish waste using an ammonia solution.
The process is simple; after the system is set up, begin by adding the ammonia solution to the water in the tank. The tank is fully cycled once the tank gets to the 0.2 ppm level. Once fully cycled, additional freshwater and fish can be added.
Ways to Reduce System Cycling Time
System cycling is a slow process, but there are other ways to establish your system quickly. One method to establish your system is to use water from another aquaponics system where the bacteria colony is already installed. It is beneficial to share a part of the biofilter as a bacteria seed to a new aquaponics system. This decreases the time necessary for cycling the system. Some prefer to add a little urea or a dead fish into the tank to start the decomposition process. Household ammonia products can also be used, but be sure that the product is 100 percent ammonia and does not include other ingredients like detergents or heavy metals that could damage the entire system.
Once ammonia and nitrite levels are below 1 ppm, you can add plants and fish to the system. Start adding the fish slowly, continue monitoring the nitrogen levels, and be prepared to water exchanges if ammonia or nitrite levels rise above 1 ppm while the system continues to cycle.
Conclusion
Bacteria are the little microscopic creatures that do all the work in an aquaponics system by converting fish waste into food that the plants can absorb. Without them, the system would fail, the fish would die, and the plants won't grow. Bacteria are equally important as fish and plants in an aquaponics system. Subscribe to our Newsletter to stay updated on all the aquaponics-related news, products, and content.
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