Dave_P
08-04-07, 09:52
The nitrogen cycle – In the world
An important area for us to understand is the 'nitrogen cycle'. Ammonia (NH3), nitrites (NO2) and nitrates (NO3) are all products produced at different times of this cycle. This cycle is happening all around us, all the time in the oceans, lakes, rivers and on land.
Nitrogen is used by living organisms to produce a number of complex organic chemicals such as amino acids and proteins.
Our atmosphere is made up of approximately 78% nitrogen gas. Nitrogen gas is fairly stable and doesn’t like reacting with other chemicals. The atmosphere is a vast store of nitrogen and there are other stores of nitrogen such as organic matter in soils and oceans.
Nitrogen gas (N2) is taken out of the atmosphere by several different ways in a process called ‘Nitrogen fixation (http://en.wikipedia.org/wiki/Nitrogen_fixation)’. Most of the Nitrogen gas converted is by biological means by prokaryotes (http://en.wikipedia.org/wiki/Prokaryote) (actinobacteria (http://en.wikipedia.org/wiki/Actinobacteria), bacteria (http://en.wikipedia.org/wiki/Bacterium)) into Ammonium (NH4). Non-biological processes include nitrogen being taken out of the atmosphere during lightning storms and industrially when producing fertiliser for example. Also Nitrogen gas is converted during the combustion of fossil fuels.
Despite the abundance in the atmosphere, most plants take up nitrogen in two forms being ammonium (NH4) and nitrate (NO3). With nitrate being the preference as ammonium is toxic in high quantities. Plants convert the nitrates into proteins and amino acids. Animals consume the plants and convert the plant forms into animal forms of proteins and amino acids.
Ammonia (NH3) is in animal waste products and dead plant or animals. This organic form is chemically modified (mineralised) into an inorganic form ammonium (NH4) by bacteria, fungi and actinobacteria (http://en.wikipedia.org/wiki/Actinobacteria) (intermediate organisms between bacteria and fungi).
Aerobic bacteria (oxygen loving) such as the genus Nitrosomonas and Nitrosococcus then convert the ammonium (NH4) into nitrites (NO2). Bacteria mainly of the Nitrobacter genus then convert nitrites (NO2) into nitrates (NO3). These bacteria also use carbon dioxide (CO2) as their carbon source for growth. In most environments these bacteria are usually found together. This process is called Nitrification (http://en.wikipedia.org/wiki/Nitrification).
Nitrates (NO3) are then taken up plant life, but a proportion is converted into nitrogen gas (N2) or nitrous gas (N20) by bacteria in an anaerobic environment (oxygen depleted) and also cyanobacteria in aerobic conditions. This process (called Denitrificition (http://en.wikipedia.org/wiki/Denitrification)) occurs in the soil, fresh water rivers and lakes, groundwater and in the ocean. Both of these gases then enter the atmosphere.
On land masses a proportion of the nitrates enter the groundwater system and eventually end up in the oceans, lakes and rivers.
Nitrogen cycle – in your tank
As already said, the nitrogen cycle happens all around us, all of the time. It’s this cycle that we rely on in our reef tank. If it didn’t take place, the tank would quickly build up with ammonia (NH3) and kill all life in it.
Within the confines of a tank, we are putting a large number of organisms into a small space. These animals are producing waste. It’s not only the animals that we see, there is plenty of microscopic life all going through their own life cycles and organic waste material is building up.
So we need to improve the living areas of the nitrifying bacteria with the hope that the population will increase sufficiently to meet the ammonium being produced in the tank.
Any surface within the aquarium whether it be the glass, the sand etc, in fact everywhere will harbor aerobic bacteria. What we need to do is increase the surface areas within the tank to provide areas for the aerobic bacteria to multiply. It’s on this basis that most biological filter systems work whether it be undergravel, bioballs, siporax, sponges or liverock. In fact any medium will work, as all you need provide is water rich in oxygen and ammonium going over a surface. What makes one medium better than another is the amount of surface area you have in a given volume.
Nitrates are not toxic to the aquarium inhabitants unless at very high levels. The issue with nitrates is that they are one of the major nutrients that most plant life needs to grow. Also some corals, especially those that calcify, harbor zooxanthellae (http://en.wikipedia.org/wiki/Zooxanthella). Elevated levels of nitrates increase the growth rate of zooxanthellae, which in turn decreases the growth rate of the host coral.
High algae growth and stunted coral growth rates are not something we want in our reef tank. So we need to keep the nitrates levels in check.
This can be done with by providing the ideal environment for anaerobic bacteria (oxygen hating). Unfortunately medias such as bioballs, siporax and sponges are not very good environments for anaerobic bacteria. So they are good at reducing ammonium to nitrates, but not very good at reducing nitrates. Hence why you see it mentioned that they are nitrate factories.
Fortunately for us liverock provides a good environment for both aerobic and anaerobic bacteria, which is why it is recommended that this is put into your aquarium. Liverock provides many nooks and crannies where bacteria can colonise.
Recent theory suggests that aerobic bacteria colonises calcium surfaces in layers. The top most layers of bacteria then consumes all available oxygen and suffocates the bacteria on the bottom most layers. This then creates an environment underneath the layers for anaerobic bacteria to colonise. The layers build up and areas become unstable flaking away to provide food for filter feeders and corals or exported from the aquarium via the protein skimmer.
There are various other methods that are normally combined with liverock to reduce nitrates such as deep sand beds (DSB) and algae scrubbers. Protein skimmers also take out the organic substances prior to them entering the nitrogen cycle in your tank.
David Pugh (Dave_P (http://www.ultimatereef.net/forums/member.php?u=15645))
_____________________
UR.com Team
Copyright © 2007 UltimateReef.com (http://www.ultimatereef.net/forums/showthread.php?t=190134)
An important area for us to understand is the 'nitrogen cycle'. Ammonia (NH3), nitrites (NO2) and nitrates (NO3) are all products produced at different times of this cycle. This cycle is happening all around us, all the time in the oceans, lakes, rivers and on land.
Nitrogen is used by living organisms to produce a number of complex organic chemicals such as amino acids and proteins.
Our atmosphere is made up of approximately 78% nitrogen gas. Nitrogen gas is fairly stable and doesn’t like reacting with other chemicals. The atmosphere is a vast store of nitrogen and there are other stores of nitrogen such as organic matter in soils and oceans.
Nitrogen gas (N2) is taken out of the atmosphere by several different ways in a process called ‘Nitrogen fixation (http://en.wikipedia.org/wiki/Nitrogen_fixation)’. Most of the Nitrogen gas converted is by biological means by prokaryotes (http://en.wikipedia.org/wiki/Prokaryote) (actinobacteria (http://en.wikipedia.org/wiki/Actinobacteria), bacteria (http://en.wikipedia.org/wiki/Bacterium)) into Ammonium (NH4). Non-biological processes include nitrogen being taken out of the atmosphere during lightning storms and industrially when producing fertiliser for example. Also Nitrogen gas is converted during the combustion of fossil fuels.
Despite the abundance in the atmosphere, most plants take up nitrogen in two forms being ammonium (NH4) and nitrate (NO3). With nitrate being the preference as ammonium is toxic in high quantities. Plants convert the nitrates into proteins and amino acids. Animals consume the plants and convert the plant forms into animal forms of proteins and amino acids.
Ammonia (NH3) is in animal waste products and dead plant or animals. This organic form is chemically modified (mineralised) into an inorganic form ammonium (NH4) by bacteria, fungi and actinobacteria (http://en.wikipedia.org/wiki/Actinobacteria) (intermediate organisms between bacteria and fungi).
Aerobic bacteria (oxygen loving) such as the genus Nitrosomonas and Nitrosococcus then convert the ammonium (NH4) into nitrites (NO2). Bacteria mainly of the Nitrobacter genus then convert nitrites (NO2) into nitrates (NO3). These bacteria also use carbon dioxide (CO2) as their carbon source for growth. In most environments these bacteria are usually found together. This process is called Nitrification (http://en.wikipedia.org/wiki/Nitrification).
Nitrates (NO3) are then taken up plant life, but a proportion is converted into nitrogen gas (N2) or nitrous gas (N20) by bacteria in an anaerobic environment (oxygen depleted) and also cyanobacteria in aerobic conditions. This process (called Denitrificition (http://en.wikipedia.org/wiki/Denitrification)) occurs in the soil, fresh water rivers and lakes, groundwater and in the ocean. Both of these gases then enter the atmosphere.
On land masses a proportion of the nitrates enter the groundwater system and eventually end up in the oceans, lakes and rivers.
Nitrogen cycle – in your tank
As already said, the nitrogen cycle happens all around us, all of the time. It’s this cycle that we rely on in our reef tank. If it didn’t take place, the tank would quickly build up with ammonia (NH3) and kill all life in it.
Within the confines of a tank, we are putting a large number of organisms into a small space. These animals are producing waste. It’s not only the animals that we see, there is plenty of microscopic life all going through their own life cycles and organic waste material is building up.
So we need to improve the living areas of the nitrifying bacteria with the hope that the population will increase sufficiently to meet the ammonium being produced in the tank.
Any surface within the aquarium whether it be the glass, the sand etc, in fact everywhere will harbor aerobic bacteria. What we need to do is increase the surface areas within the tank to provide areas for the aerobic bacteria to multiply. It’s on this basis that most biological filter systems work whether it be undergravel, bioballs, siporax, sponges or liverock. In fact any medium will work, as all you need provide is water rich in oxygen and ammonium going over a surface. What makes one medium better than another is the amount of surface area you have in a given volume.
Nitrates are not toxic to the aquarium inhabitants unless at very high levels. The issue with nitrates is that they are one of the major nutrients that most plant life needs to grow. Also some corals, especially those that calcify, harbor zooxanthellae (http://en.wikipedia.org/wiki/Zooxanthella). Elevated levels of nitrates increase the growth rate of zooxanthellae, which in turn decreases the growth rate of the host coral.
High algae growth and stunted coral growth rates are not something we want in our reef tank. So we need to keep the nitrates levels in check.
This can be done with by providing the ideal environment for anaerobic bacteria (oxygen hating). Unfortunately medias such as bioballs, siporax and sponges are not very good environments for anaerobic bacteria. So they are good at reducing ammonium to nitrates, but not very good at reducing nitrates. Hence why you see it mentioned that they are nitrate factories.
Fortunately for us liverock provides a good environment for both aerobic and anaerobic bacteria, which is why it is recommended that this is put into your aquarium. Liverock provides many nooks and crannies where bacteria can colonise.
Recent theory suggests that aerobic bacteria colonises calcium surfaces in layers. The top most layers of bacteria then consumes all available oxygen and suffocates the bacteria on the bottom most layers. This then creates an environment underneath the layers for anaerobic bacteria to colonise. The layers build up and areas become unstable flaking away to provide food for filter feeders and corals or exported from the aquarium via the protein skimmer.
There are various other methods that are normally combined with liverock to reduce nitrates such as deep sand beds (DSB) and algae scrubbers. Protein skimmers also take out the organic substances prior to them entering the nitrogen cycle in your tank.
David Pugh (Dave_P (http://www.ultimatereef.net/forums/member.php?u=15645))
_____________________
UR.com Team
Copyright © 2007 UltimateReef.com (http://www.ultimatereef.net/forums/showthread.php?t=190134)