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17 Oct 2008 - The Nitrogen Cycle

The Nitrogen Cycle

By Ken Thomson "aka" Kenliz

For most Fish keepers whether new or experienced in the keeping of fish in Aquariums this subject is of great importance. The maintaining of water conditions so our pets can live a good and healthy life is required. The first stage in any Aquarium is the setting up and maturing of the water. When the Aquarium is first filled with water the water should be treated to remove Chlorine and Chloramines. There are many products on sale for this purpose. If the water is not treated leave the tank to run for at least a week so that these gases can naturally dissipate from the water.

Now we can start to cycle the tank.

There are two main methods of doing this.

  1. The Fishless Cycle where Ammonia solution is added to start the cycle.
  2. The Fish cycle where hardy Fish ie; Danio's and/or Platys.

The main job of cycling a tank is to remove Ammonia and Nitrite from the tank. These come from the waste products from fish, uneaten food and decomposing plants. First Ammonia (NH3/NH4) is produced and changed to Nitrite (NO2) by Nitrosomonas bacteria. The Nitrite is then changed in to Nitrate (NO3) by Nitrobacter bacteria. Nitrates are generally a lot less harm full to the fish and are quite safe if kept to levels of 20ppm or less. Of course different Fish have different tolerance levels so remember to research any fish you may want to stock. If you decide you want to have your aquarium planted with live plants the one good thing is that they will use the Nitrates as a food source but that's another Article for another time.

Other important points to keep check on are ph of both tank and tap water plus do test your tap water for Nitrates as it's not uncommon to have up to 50ppm. Normally you don't have any problems with the ph but if you live in a Soft water area ph can crash to very low levels. By testing your water for KH (carbonate hardness) and GH (general hardness) you will be able to judge this. A KH level of 4 degrees is required for a stable ph in my experience. Again this is another article for another day.

Method one requires the adding of ammonia solution to the tank.

You build the Ammonia levels to 5ppm over three days then add daily to keep the level at 5ppm. You will decide this by taking in to account the Strength of Ammonia and size of tank (Ammonia Calculator). I usually count up the ml of Ammonia or for smaller tanks drops of Ammonia over the three days to get to 5ppm then add half of this total every day till the Nitrite level starts to show when tested. Then cut the Ammonia level added in half again till both Ammonia and Nitrite levels test zero. This can take any where between 10 days and 21 days and then your tank is cycled. The big bonus of this method is the cycle is shorter, you can stock more fish quicker and no fish are stressed out due to the cycle. When doing this method keep the temp at 81degs F and keep a close check on the ph. As a ph of 6 or under can stop the growth of the Bacteria colonies.

Now the second method.

The use of hardy fish. Normally Danio's or Platys are used for this as they can last out the cycle quite well. I normally add 1 fish per 5 gallons (imperial) of water. You add the fish and step back and keep testing the main four tests, Ammonia, Nitrite, Nitrate and ph till Ammonia and Nitrite are both zero. Points along the way your tank can and may become cloudy. This is normal and will clear. This is caused by a bacterial bloom in the water and is a good sign in a cycling tank. It will also do the fish no harm. On feeding your fish, once every second day will suffice and actually help cut down the Ammonia and Nitrite levels. Water changes should only be done if your fish are showing signs of stress. On the subject of ph just follow the same as method one. If your pH does drop some coral gravel in a sock and soaked in the tank for a couple of hours will help to bring the ph back up. I won't go any further into water hardness at this time. This method can take any where between four to six weeks and then new fish must be added slowly over a number of weeks. There are draw backs to this method. Lengths of time to cycle, longer to be fully stocked but you do have fish in the tank at an earlier stage.

Hope this helps in your understanding of the Nitrogen Cycle.

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Comments *

1) Re: The Nitrogen Cycle
Written by 0 on February 06, 2012, 08:16:08 pm
should plants enter the tank once the cycle is complete ??
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