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Ammonia and Nitrites and Nitrates, Oh My!
A Quick and Dirty Overview of the Nitrogen Cycle
BackEstablishing Nitrifying Bacteria in an Aquarium: Cycling the Tank
Establishing nitrifying bacteria in the aquarium, starting with very few bacteria to having a colony of bacteria that will reduce ammonia and nitrite to zero, is called cycling a tank. After adding water, initially the population of bacteria in the aquarium is small and incapable of handling the ammonia that will be excreted by livestock. In order to establish these bacteria, a source of ammonia must be provided. There are several methods used to cycle an aquarium.
For a fishless cycle, add ammonia and test the water. Use clear ammonia that does not contain surfactants, soaps, coloring or scents, as these may inhibit establishment of a nitrifying colony and will have negative health consequences for livestock added later. Add ammonia until a reading of approximately 5 ppm (5 mg/l) is obtained. Note the amount of ammonia that was added (in drops, mg, teaspoons or whatever measurement is used) to achieve that concentration. Add the same amount of ammonia daily. The ammonia concentration will remain steady or increase a bit, but at this time no nitrites will be detectable. Measure the ammonia and nitrites daily. Once nitrites appear, reduce the addition of ammonia to half of the amount added initially (for example (6 ml would be reduced to 3 ml). Nitrites will rise to a concentration similar to those of the ammonia. At some point the concentrations of both the ammonia and nitrite will begin to decrease. Continue adding the half dose of ammonia daily until no ammonia or nitrites are detectable. At this point, cycling is complete. A water change of 90% to 100% is recommended to remove the nitrates that have built up in the aquarium during the cycling process, and then livestock may be added.
To cycle with fish, add one or two hardy fish and test the nitrite and ammonia daily as above. The same increases and spikes as described for a fishless cycle will be seen in both followed by an eventual decrease to no ammonia and nitrites. When cycling with fish, a daily water change of 50% should be conducted, to make the process easier on the critters.
A third method used is to add fish food to an empty tank, allowing the decomposition of the food to be the ammonia source. A small amount of food is added daily and testing proceeds the same way as in the previous methods until no ammonia or nitrites are detectable.
To speed up the process, gravel, decorations or other objects from an established aquarium can be added to seed the new aquarium by introducing a large number of bacteria immediately. This can speed up the cycling time immensely. A sponge filter or a filter pad from a hang on back filter that has been used in an established could also be used to seed the tank. Another method of speeding the cycle is to use an aquarium product that adds bacteria to the tank. Usually these are sold in a liquid form and are available from most pet stores.
Live plants may be added to an aquarium immediately, prior to stocking. This may also speed the cycle.
The length of time to fully cycle a tank varies but without seeding may take 4-8 weeks. Seeding may shorten the process to a week or even less. Regardless, once the ammonia and nitrite read 0 ppm, the fun part begins. Ya can add critters!
In Closing...This may have been far more than many hobbyists care to know. It attempts to provide background on the nitrification cycle, how it works, and how it applies in an aquarium, as well as answer many of the frequent questions I have asked or have been asked through the years. Please feel free to take what ya need and ignore the rest.
One final note. The list of papers, individuals, and other resources that provided information used in this article is extensive and a bibliography would likely run a dozen pages or more. I understand that there are inconsistencies within the literature, and some of what has been stated can be supported in one paper and contradicted in another. The point of this article, however, is not to nitpick whether Nitrosomonas reproduces faster at 78 or 80 degrees, but to provide a baseline understanding of the topic for the aquarium hobbyist.
May all yer tanks nitrify!
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