Nitrification (or nitrogen) cycle
It is important to cycle your tank BEFORE you add any fish as the cycling process involves high levels of ammonia and nitrite that can cause considerable damage and possibly death to your fish. That said some people prefer to use a method involving adding hardy fish to set up a new aquarium.
First it is important to understand the process.
The nitrogen cycle is the process that ‘gives birth’ to the bacteria needed to help break down the ammonia and nitrite produced by your fish through waste (pee and poo).
There are three components needed to do this: ammonia (NH3, NH4), nitrite (NO2) and nitrate (NO3). Ammonia and nitrite are harmful to your fish and must both read 0 in a cycled tank. Nitrate is not as harmful but will still cause stress and is best to keep it under 20ppm (parts per million) in a cycled tank.
The time it takes to cycle your tank can vary depending on different factors, in general it will take approximately 2 – 6 weeks. It is important to regularly test your ammonia, nitrite and nitrate parameters to monitor the phase the cycling is in.
Ammonia will increase over a period of 14 days before aerobic bacteria called nitrosomonas europaea will grow in your filters in a sufficient number to convert ammonia into nitrite. When this happens ammonia levels will decrease rapidly and nitrite levels will slowly increase. The nitrite levels will increase over a period of 14 days before aerobic bacteria called nitrobacters will grow in your filters in a sufficient number to convert nitrite into nitrate. When this happens nitrite levels will decrease rapidly and nitrate levels will slowly increase. Once at this point your tank is cycled. You may need to do a water change of about 50% to bring the nitrates down to the recommended level before you add any fish. Nitrate is relatively harmless to your fish but the recommended ‘safe’ level is below 20 ppm. All that is needed now is regular weekly water changes to keep nitrates under that level.
Fishless cycle (using ammonia)
Set up your tank, including all filters, heater, light and protein skimmer for marine tanks.
Start the filters and heater, setting the temperature at 80 F (or 26 C).
Once set up add 5 drops of ammonia per 10 gallons on a daily basis until the reading has reached 5ppm or higher. You should then be getting a reading of nitrite, once this happens reduce the ammonia to 3 drops per day. Nitrite levels should then rise to 5ppm or higher. Keep adding 2 – 3 drops of ammonia until ammonia and nitrite levels read 0. The tank will now be cycled. Do a water change of about 25% to bring your nitrates down to below 20ppm and you can now add your fish. If you add your fish all at once it may cause your tank to go into a mini cycle. So patience is important, only add a few fish at a time, until you reach the bio load recommendations for your tank size.
NB: It is possible to add too much ammonia to your tank. If your readings of ammonia and nitrite are off the charts do a water change, or series of water changes if necessary to bring your reading down to about 5ppm, then proceed with daily ammonia addition.
Things to keep in mind: your tank needs sufficient filtration for the oxygen needed by the bacteria, you should only use pure ammonia, it should not have any additives or perfumes, this may slow the process, and don’t use conditioners that remove ammonia, it will eliminate the ammonia you are adding and thus your tank will not cycle. In some aquariums you may still lack the beneficial bacteria required and the tank may go into a mini cycle when fish are added.
There are methods to help the process along such as adding gravel or filter media from an established tank. You could also add potted plants to help the process along.
If you are not adding fish straight away it is important to keep feeding your tank, otherwise the bacteria will die off and you will need to re-cycle your tank before adding fish, or if you add fish your tank will go into a cycle.
Fishless cycling (using fish food)
Set up the tank as in the ammonia method.
It is recommended to add gravel or filter media from an established tank to help with the process, but not necessary if you cannot obtain it.
Then you simply add fish food for a first dose, then small amounts daily. As the food decays it produces ammonia and starts the cycling process. Doing regular checks of ammonia and nitrite levels will help you know what stage the cycling is at.
It should take about the same time as other methods if done correctly.
NB: There is a significant risk that the decaying food will produce phosphates as a by-product.
Again you may lack enough of the beneficial bacteria in your tank and when you add fish it will go into a mini cycle.
Again if you are not adding fish straight away it is important to keep feeding your tank.
Cycling using fish
Set up your tank as above.
Again it is beneficial if you can add gravel or filter media from an established tank.
Add hardy fish and let nature take its course. Remembering to feed the fish in order for them to produce waste, which in turn produces ammonia and starts the cycling process. Again keep doing regular checks of ammonia and nitrite levels to check which phase the cycling is up to. When the nitrite spikes do a small water change, about 20%. Then leave it, and remember to do regular checks of nitrite and nitrate. When you get no nitrite reading and nitrates start increasing do another 20% water change. Then do regular weekly changes of 25% to keep nitrate at ‘safe’ levels.
It should take around the same time as the other methods.
NB: Ammonia and nitrite are extremely harmful to your fish. Using fish during the cycling process may end with the fish dying, or having severe damage to their immune system thus making them susceptible to various diseases. Therefore do not use the fish you intend to keep permanently.
Edited by mrs winchester, 29 December 2007 - 02:48 AM.