Introduction to Aquaponics
Nitrogen Cycle
The Nitrogen cycle is the most
significant process within Aquaponics as it is responsible for the conversion
of fish waste into nutrients for the plants, and without this process, the
water quality would deteriorate rapidly and become toxic to both the fish and
plants in the system.
Nitrogen is a fundamental element that is necessary for all forms of life on Earth, as it is an important component in both plant and animal cells, so organisms need nitrogen to produce proteins, nucleic acids, and amino acids.
Although Nitrogen gas (N2) is roughly 78% of the earth’s atmosphere, it is unusable in this form, so the majority of organisms on earth can only use nitrogen when it is ‘fixed’ – combined with carbon, hydrogen or oxygen.
In Aquaponics, a system is said to have ‘cycled’ when there are sufficient quantities of bacteria to convert all the ammonia into an accessible form of nitrogen for the plants.
The bacteria will arrive naturally to a system and colonize the water column and biofilter (usually clay pebbles, gravel or netting).
Nitrogen is a fundamental element that is necessary for all forms of life on Earth, as it is an important component in both plant and animal cells, so organisms need nitrogen to produce proteins, nucleic acids, and amino acids.
Although Nitrogen gas (N2) is roughly 78% of the earth’s atmosphere, it is unusable in this form, so the majority of organisms on earth can only use nitrogen when it is ‘fixed’ – combined with carbon, hydrogen or oxygen.
In Aquaponics, a system is said to have ‘cycled’ when there are sufficient quantities of bacteria to convert all the ammonia into an accessible form of nitrogen for the plants.
The bacteria will arrive naturally to a system and colonize the water column and biofilter (usually clay pebbles, gravel or netting).
The nitrification cycle is the process by which the ammonia produced by the fish is converted by one type of bacteria to nitrite and then by another type of bacteria to nitrate (the most plant-accessible form of Nitrogen in the cycle – and safest for the fish).
The two types of bacteria that break down ammonia (NH3) and nitrite (NO2) are :.
When all these bacteria are found in sufficient numbers in order to convert all of the ammonia and nitrite being produced in a system, it is said to have ‘cycled’.
The two types of bacteria that break down ammonia (NH3) and nitrite (NO2) are :.
- The Nitrosomonas bacteria convert the ammonia into nitrite and then the Nitrobacter bacteria converts the nitrite into nitrate (NO3). Nitrosomonas sp. – This bacterium takes in ammonia and converts it to nitrite. Nitrite is the less poisonous compound for the fish than ammonia would be. However, high levels of nitrite will prevent the fish from taking up oxygen and will cause damage to their gills.
- The Nitrobacter sp. is the next bacterium in the cycle and it consumes nitrite and converts it to nitrate. Nitrate is a very accessible nutrient source for plants. Fish will also tolerate a much higher level of nitrate than they will ammonia or nitrite.
When all these bacteria are found in sufficient numbers in order to convert all of the ammonia and nitrite being produced in a system, it is said to have ‘cycled’.
The water in Aquaponics does not need to be treated chemically to make it ‘safe’ nor does it have to be replaced.