Setting-Up Fish Tank Aquariums: The Nitrogen Cycle Explained
The Nitrogen Cycle Explained
The Nitrogen Cycle is merely a method of starting an aquarium. Learning what it is, and how to deal with crucial periods during the nitrogen cycle, will decide the success of your tank aquariums. All new tank aquariums go through a process of establishing valuable bacterial colonies in the aquarium and in the filter media which get rid of waste and thereby maintain a healthy ecosystem. These bacteria convert ammonia –> nitrite –>nitrate. This normal process takes between 2-8 weeks, depending on the size of the aquarium.
The Earliest Stage – Ammonia
The faeces and urine of fish in addition to uneaten food are rapidly broken down into either ammonium (water pH below 7) or ammonia (water pH above 7). Ammonium is not harmful to fish but ammonia is. In nature, the amount of water per fish is tremendously high, and waste products become diluted to low concentrations. In the stagnant and limited quantity of water in fish tank aquariums, however, it can take as little as a few hours for ammonia concentrations to arrive at lethal levels. Once a test kit is able to detect ammonia there is too much! Ammonia burns the gills of the fish and starves the water of oxygen. Fortunately bacteria that are capable of converting wastes to safer by-products commence growing in the tank. This takes time and requires thorough monitoring and patience.
The Second Stage – Nitrites
In the second stage of the nitrogen cycle, Nitrosomonas bacteria grow which oxidize the ammonia and eliminate it. On the other hand, the by-product of ammonia oxidation is nitrite, which is also very toxic to fish, damaging the central nervous system. Using a test kit, you should be able to see the nitrite levels increase around the end of the first or second week.
The Third Stage – Nitrates
In the final stage, Nitrospira bacteria start developing that use nitrite and change it into nitrate, which is not toxic to fish in small quantities. (Nitrobacter bacteria were formerly believed to convert nitrites to nitrates but current research has shown they are not present in noticeable levels in established fish tank aquariums, while Nitrospira are bountiful.)
Test, Test, Test!
It is essential to obtain appropriate test kits to evaluate the levels of ammonia, nitrites and nitrates throughout the cycle. You should test the aquarium water every other day and write down your readings. You will know when the nitrogen cycle has completed by reading the levels of ammonia, nitrite and nitrate in the water. When the first two readings hit 0 and the nitrate reading levels are around 10, your tank is all set for fish. Be wise though, to only put in a couple at a time, otherwise the readings will start climbing again with the increased bio-load.
Ways to Start the Nitrogen Cycle
Using Fish
The former method is to select a couple of small, hardy fish such as Zebra Danios. This is not the preferred way to get the nitrogen cycle on track because the fish are being exposed to ammonia and nitrites causing them stress and even sickness and death. It is of the essence to keep testing the water and carefully observing the fish. If at whatever time fish exhibit signs of distress such as rapid breathing, clamped fins, erratic swimming or hanging at the surface for air, do an immediate 50% water change. Do not over-feed the fish and do not add more fish until the cycle is completed.
Not Using Fish
The fishless cycle is a brilliant method to start tank aquariums, and involves no potential danger to fish, as they are not used. The creation of ammonia can be achieved by dropping fish food into the tank every 12 hours or by leaving a tiny piece of raw fish in the tank. As either decomposes it will release ammonia.
On the other hand, the same effect can be achieved by adding chemical forms of ammonia yourself. The water chemistry needs to be monitored closely in order to add the appropriate amount of ammonia on a day-to-day basis into the tank. It is suggested to start with 5 drops of ammonia per 10 gallons of aquarium water and then reduce this to 3 drops once you can detect nitrites. If you had to use more drops than 5 to get an ammonia reading, then cut the number of drops in half when you get nitrite readings. Continue this process daily until you get nitrate readings with your test kit. After a 30% water change the tank should be ready to start slowly adding fish.
Speeding Up the Nitrogen Cycle
To hurry along the process of cycling tank aquariums some beneficial bacteria colonies can be obtained from an already established and cycled aquarium and placed in the new tank. This can be obtained by putting gravel from an established aquarium into the new tank or filling the new aquarium with water from an established aquarium.
Since the biggest bacterial populations are found in the filter, a more effective way is to borrow an extra filter from an established tank and run it in the new tank for a few days, or to place used filter media into the new filter. This will seed the tank with all the necessary bacteria for the nitrogen cycle.
More recently, there are products on the market which some aquarists have found helpful in introducing the beneficial bacteria e.g. Bio-Spira, Colonize, Cycle, Stability and Septo-Bac.
Keep Nitrates Low
Once freshwater aquariums are established, they can still go through periods during which the bacterial colonies fluctuate. Established tank aquariums should be tested for nitrates every few months to ensure that levels are not becoming dangerously high. The quickest way to rid tank aquariums of nitrates is to carry out partial water changes. A 25% weekly water change is a common recommendation.
Keep the Good Bacteria Growing!
It is important to be aware of the following advice so that you continue to encourage the growth of beneficial bacteria.
Never add chlorinated water directly to tropical freshwater fish tank aquariums as the chlorine in tap water will exterminate the beneficial bacteria instantly resulting in an explosion of ammonia and nitrites; that means you will have to commence all over again! Allow water to remain in a bucket with an aerator for some time before adding to the aquarium.
Another common problem is that people over clean their tanks during partial water changes and maintenance. Never douse the filter media with standard tap water if it becomes blocked. Instead, rinse the filter media in tank water.
Only add new fish one pair at a time to an aquarium as the load from too many fish overwhelms the bacteria colony’s ability to manage it. Also do not over-feed fish as the bacteria might not be able to take the added load of excrement.
If you are treating fish for infection, treat them with antibiotics in a bucket of water. Adding antibiotics to the aquarium kills all the beneficial bacteria.
You Can Do It!
When you have a grasp of how the nitrogen cycle works and the steps to take, you will be successful in dealing with the challenges it presents and establishing the attractive fish tank aquariums you desire.
Copyright © 2009 Jill Kaestner @ Kaestner Marketing LLC
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