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Ways how to Cycle an Aquarium

The key aspect of fish keeping has to be cycling your aquarium ready for the arrival of your first fish. If you have researched you will know that the water parameters need to be perfect for your fish and that the filters need to be capable of handling the bio-load created by the fish expelling their waste into the aquarium and from rotting plants decaying. It is crucial that your water is tested on a regular basis so investing in a quality testing kit is a good investment especially in the early days of your aquarium running. Nowadays most keepers will perform the aquarium cycling without using hardy fish to build up the filters but some still do so both methods will be explained in this article.

Aquarium cycling with fish

This method is used for keepers who are adding fish to their aquariums straight away, the fish used must be very hardy as sensitive fish will suffer during this cycling method. If possible try to get hold of some filter media from an established aquarium and add it to your filter, this will kick off the cycling process straight away. If you cannot get any media it will mean that the aquarium cycling process will take longer, anything up to 6 weeks. Once the hardy fish are added to the tank you will start to get ammonia readings with your test kit. These readings will continue to rise as the bacteria in the filter are still colonising and until the colony is large enough they will not be able to cope. Once the ammonia has peaked the ammonia results will start to drop and the readings of nitrites in the water will start to rise. This will mean that the bacteria which convert the ammonia into nitrites have now colonised to a large enough colony to deal with the first part of the aquarium cycling.

Eventually the readings for nitrites will peak and drop to 0, this means that the beneficial bacteria are now converting the nitrites into nitrates, these are less toxic than ammonia and nitrites so now you are well on the way to your aquarium cycle being completed. The only way to remove nitrates is to perform regular water changes so now is the time to start this, readings of below 40 for nitrates means that the aquarium is cycled and you will now need to keep performing your water changes to keep the nitrates at a constant level.

Key points to remember with this method of cycling are:-

Aquarium cycling-the fishless method

This is the preferred method on most fish keepers nowadays, the aquarium can be cycled without placing any possible stress on fish and will often provide stronger bacterial colonies in the aquarium filters. It can be achieved by three different methods but the results will always be the same. Commercial bacteria cultures can be used, these are simply added to the aquarium following the instructions on the bottle, these work for some keepers bot some are biased against them. The second method is to add some fish food to the aquarium and allow it to decay thus producing ammonia, this method does work but controlling the ammonia levels in the aquarium is a bit hit and miss. I much prefer using pure ammonia, you know exactly how much is being added to the aquarium and you can control the levels to suit the stage of the aquarium cycle. This is the method I will explain below:-

The ammonia used must be pure, there are perfumed ammonia bottles for sale, these will not be suitable for the aquarium as they will add harmful toxins to the water that will remain after the cycle has been completed. Using the pure ammonia add a few drops at a time, with the first dose you will have to repeatedly test the water with a suitable testing kit until you reach an ammonia level of 4-6 ppm. Do not test the water as soon as you have added the ammonia, stir the water and test after an hour. Count how many drops it took to reach the required level, this will help you work out how much ammonia is needed with each dosing. Repeat this process every day until the ammonia readings start dropping when you are still adding the same dosage, this means that the ammonia has peaked and bacteria are now converting this to nitrites. Now is the time to start testing for these with your testing kit.

After a few days of repeatedly dosing your tank the nitrites should also start to drop, nitrates are now in the aquarium water, test for nitrates to check on this. Once nitrates are in the water your aquarium cycle is nearly complete. The nitrites will drop to zero and the nitrates can be removed by regular water changes. Now your filters are ready for fish to be added to the tank!

There are a couple of points to remember using either method of cycling your aquarium:-

Questions and answers

On March 18th 2011 we merged all related questions and answers from with this article in order to put all related information together. Some of the answers listed below may have been answered partially in the article above, however it's easier to find a particular answer within a list instead of sentences in text. All questions were asked by visitors of Aqua-Fish.Net and you're welcome to ask too! Simply fill the form at the bottom of this page and ensure that you're asking something that isn't answered here yet.

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