Retract and activate the biofilter

The nitrification process in aquaponics

Ammonia ⇒ Nitrite ⇒ Nitrate
The nitrifying bacteria play an important role in an aquaponics system. They convert fish waste so that ammonia enters the system as nitrate. Nitrification in aquaponics is a two-step process and involves two nitrifying bacteria:

1. Conversion of Ammonia to Nitrites – This is carried out by the Nitrosomonas when there is an overload of food waste, it produces excess ammonia in the water. The ammonia must be removed to keep the fish healthy. Nitrosomonas bacteria convert the ammonia into nitrites.

2. Conversion of nitrites to nitrate – This is carried out by Nitrobacter . Nitrobacter bacteria feed on nitrites. The nitrites are converted into nitrates once the nitrites are consumed by Nitrobacter. Plants grow quickly when they absorb nitrates. Excessive nitrites can kill the fish. In order to keep the fish and plants healthy, nitrites must be converted into nitrates.

Nitrifying bacteria multiply slowly and form colonies; It can take days, weeks, or even months. Nitrifying bacteria require a dark location, good water quality, and sufficient food and oxygen to colonize. There are five key parameters to support nitrifying bacteria. If these parameters are met, it can be assumed that the bacteria are present and functioning well.

1. Large surface area

Biofiltration with a high specific surface area is important to develop extensive colonies of nitrifying bacteria. There are many materials that can be used in aquaponics, either as growing media or for biofiltration. Volcanic gravel, expanded clay pebbles, commercial plastic biofilter balls, and plant roots all act as a surface for the bacteria to live on. The smaller and more porous the particles, the larger the surface area available for bacteria to colonize, resulting in more efficient biofiltration.

2. Water pH

Nitrifying bacteria function properly when the pH is between 6 and 8.5. The ideal pH in aquaponics is usually 6-7, which is a compromise between all organisms in the system.

3. Water temperature

The ideal temperature range for the bacteria is between 17° Celsius to 34° Celsius (~ 63°F - 93°F). This area promotes the growth and productivity of bacteria. If the water temperature drops below this range, it reduces the productivity of the bacteria. If it rises far above this (42 °C), the bacteria die.

4. Dissolved oxygen

Nitrifying bacteria require sufficient levels of dissolved oxygen in the water to grow healthily and maintain productivity. The optimal dissolved oxygen level is 4 - 8 ppm, nitrification does not occur if the dissolved oxygen concentration falls below 7.0 ppm. You can ensure adequate biofiltration and dissolved oxygen by adding aeration, either using air stones or through flood-and-drain cycles in media beds.

5. No UV light

Nitrifying bacteria are sensitive to light until they are fully established. and sunlight can damage the biofilter. Media beds protect the bacteria from sunlight, but if you use a biofilter, protect it from direct sunlight.

Undesirable Bacteria
Nitrifying and mineralizing bacteria are important and useful for aquaponics, but there are some types of bacteria that are harmful to an aquaponics system, these are:

1.Sulphate reducing bacteria

These bacteria are often found in anaerobic conditions and smell like rotten eggs. These bacteria are gray-black in color and only grow under anoxic conditions. It is important to provide adequate ventilation and increase mechanical filtration to prevent the accumulation of these bacteria.

2. Denitrifying bacteria

These bacteria also thrive in anaerobic conditions and are responsible for denitrification. They convert nitrites back into atmospheric nitrogen, which is not available to plants. In aquaponics systems, these bacteria can reduce efficiency by removing the nitrogen fertilizer.

3. Pathogenic bacteria

These bacteria can cause diseases in plants for fish and humans. It is important to have good practices ( CMMI ) to minimize the risk of disease in an aquaponics system. You can prevent pathogens from entering the system by keeping all other animals (pets, farm animals, etc.) away from your system. Placing your aquaponics system in a closed greenhouse can also prevent pathogenic bacteria get into your system.

System Cycling and Creating a Biofilter Colony
System cycling in aquaponics refers to creating a healthy bacterial colony when you start your new aquaponics system. The process takes place once a new aquaponics system is built and typically takes 4 weeks to two years. The process involves introducing a source of ammonia (usually fish) into a new aquaponics system, feeding the new bacterial colony, and building the biofilter (by the bacteria themselves). Progress is measured by monitoring nitrogen levels.

Without bacteria, the nitrogen cycle does not take place. The nitrogen cycle converts the ammonia from fish waste into nutrient-rich fertilizer for plants. The nitrogen cycle only occurs when the nitrifying bacteria are present. In order for this to take place, ammonia must be added to the system. This ammonia can be added with the fish or with water from another aquaponics system where the bacterial colony is already established. When more ammonia is added, more bacteria are produced, making the system work more efficiently. Once ammonia-converting bacteria become established, they produce nitrites, which allows the bacteria to use the nitrites and produce nitrates from them. A system is fully established (broken in) once ammonia or nitrites are measurable during the test.

This process is often used in new aquaponics systems or tanks because it can be done without concerns about fish safety. To begin fishless cycling, you need to introduce ammonia into the system.

The process is simple; After the system is set up, begin adding the ammonia solution to the water. Once the system (tank, pumps, etc.) has been completely circulated, you should have achieved at least a value of 0.2 ppm.

Ways to Reduce System Cycle Time
System cycle is a very slow process. Depending on the size and type of system, the process can take up to 18 months. However, there are other ways to set up the system faster. One method is to use water from another aquaponics system where the bacterial colony is already established. It is helpful to pass part of the biofilter as a bacterial strain to a new aquaponics system. This reduces the time required to go through the system. Some prefer to add a little urea or a dead fish to the tank to start the decomposition process. But pay attention to the formation of pathogenic bacteria - you must avoid these. Household ammonia can also be used. However, make sure the product is 100 percent ammonia and does not contain other ingredients such as detergents or heavy metals that could damage the entire system.

Once the ammonia and nitrite levels are below 1 ppm you can add plants and fish to the system. Start with a few fish and closely monitor nitrogen levels. Be prepared to replace the water if ammonia or nitrite levels rise above 1 ppm while the system continues to run.

Conclusion
Bacteria are the little microscopic creatures that do all the work in an aquaponics system by converting fish waste into nutrients that the plants can absorb. Without them, the system would fail, the fish would die and the plants would not grow or die completely. Bacteria are just as important in an aquaponics system as the fish and the plants. 

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