The Nitrogen Cycle breaks down fish waste and bacteria into nonharmful substances. This is essential for the survival of your aquarium fish.
When fish eat they excrete ammonia into the water. This ammonia is poisonous to fish. In a cycling tank, beneficial bacteria (nitrifying bacteria) consume this ammonia and convert it to nitrite.
Process
As fish waste and decaying food break down in an aquarium, ammonia is produced. Ammonia is toxic to fish and can burn their gills, so it must be converted into something less harmful by beneficial bacteria. This process is called the nitrogen cycle. The process usually occurs organically in nature as fish and other organisms produce their own waste, but since an aquarium locks the water into one place the nitrogen cycle needs to be established artificially.
The first step in the process is to add a source of ammonia to the tank. The ammonia is broken down by a chemical reaction with bacteria called Nitrosomonas, which releases nitrites. Another type of bacterium, called Nitrifying Bacteria, then converts the nitrites into nitrates. Finally, algae or underwater plant life consumes the nitrates and produces oxygen.
It is very important that a new aquarium be properly “cycled” before adding fish to it. If the aquarium is not cycled, ammonia and nitrite levels will build to dangerously high concentrations that can poison or kill the fish. The best way to cycle a new aquarium is to use the method of stocking it slowly over time with smaller fish and adding a bacterial starter like Fritz Zyme or Stability.
Be careful not to rinse the filter media with tap water because chlorine can kill beneficial bacteria that are needed for the nitrogen cycle. It is also recommended that you do not tamper with the pH of the aquarium until after the Nitrogen Cycle is complete.
Beneficial Bacteria
A healthy aquarium depends on beneficial bacteria to break down fish waste, dead plant material and other organic debris. These bacteria convert toxic ammonia and nitrite into non-toxic nitrate. They also help remove heavy dissolved organic loads from the water, and can reduce phosphate levels. These obligately aerobic, heterotrophic bacteria (that means they need to eat other things) live in the filter media and on solid surfaces in the tank such as gravel, rocks, decorations and plants, but it takes quite a bit of water flow through these be nuoi ca spaces and some time for them to establish themselves.
The nitrogen cycle usually happens naturally as animals create waste and nature cleans it up, but an aquarium locks the fish in one place and must have a different process to ensure safe water. When fish produce waste, that waste contains bacteria that are harmful to them if they are exposed to it. The nitrogen cycle breaks down that harmful bacteria and makes the water safer for the fish.
There are many products on the market that claim to “seed” an aquarium with these nitrifying bacteria, but the best way to start the Nitrogen Cycle is by doing regular water changes and using a well-made filter that can handle the load. The nitrifying bacteria are actually all around us, and can be found in the air. It just takes a while for them to grow enough to get the nitrogen cycle going.
Ammonia Control
Ammonia levels in a fish tank are best controlled by using regular partial water changes. When performing these water changes, try to use a small scoop or a bucket to replace the water, rather than dumping out the whole contents of the tank. This will help to minimize disturbing the substrate. Depending on how high the ammonia level is, it may be necessary to perform these water changes more frequently.
Another way to control ammonia levels is by reducing fish feeding. The protein found in fish food is broken down in the digestive tract and produces ammonia. This ammonia is then excreted in the urine, and also breaks down into nitrites. Nitrites are then converted to nitrates by a different set of bacteria. This process is part of the aquarium’s nitrogen cycle.
Both groups of nitrifying bacteria require oxygen to function and grow. If the aquarium’s oxygen levels drop, these bacteria will stop functioning or die. These bacteria also need alkalinity to function. If the alkalinity in the water decreases, nitrifying bacteria will stop functioning and ammonia will increase.
When cycling a new aquarium, the ammonia level should be kept low by performing regular water changes. Adding live aquatic plants and liquid starter solutions will also help to keep ammonia levels down. These products will introduce good bacteria to the filter medium and substrate, allowing them to break down ammonia faster.
Aquarium Water Quality Maintenance
Keeping healthy water in an aquarium requires consistent monitoring of pH, Ammonia, Nitrite and Nitrate. These are natural chemicals produced by fish waste, food and decomposing organic material, but in high levels they can kill fish and other animals in the tank. Regular testing can help you spot these spikes quickly.
All new fish tanks go through a process of establishing beneficial bacterial colonies and getting their filtration systems up to speed. This is called the “cycling” or “nitrogen cycle”, and it can take a while to achieve in new aquariums. Even older aquariums can experience cycling periods from time to time.
The bacterial colony consumes ammonia through its own natural respiration, and it converts it to nitrite via nitrification. Nitrite is then converted to nitrate by other bacteria in the aquarium’s filtration system. Nitrate is toxic to fish, as it inhibits oxygen exchange in their bloodstream, causing them to suffocate. Nitrate should be kept below 5 ppm in freshwater, and 0 ppm in marine and reef systems.
The best way to determine the type of water quality maintenance you need is to use a test kit. Choose the appropriate kit for your aquarium’s water type (Freshwater, Saltwater or Reef) and follow its instructions. Depending on the method you choose to cycle your tank, you will need to monitor ammonia and nitrite daily, and do a water change whenever readings are above zero.