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Nitrogen cycle the fishless way

Updated on July 3, 2013

Importance of nitrogen cycle

Aquarist had always been reminded regarding nitrogen cycle either for freshwater aquarium or saltwater aquarium. Is that so important? Well, indeed Nitrogen cycle is one of the most important elements to be taken care of if you really serious about fish well being. Water quality will deteriorates when fish introduced to aquarium. It is inevitable as waste will be excreted from fish as well as from plants and the detritus will decomposed and become toxic waste. Thus a colony of nitrifying bacteria is essential to ensure health of the aquarium.

Nitrogen cycle process


The whole nitrogen cycle occurred when there is a presence of ammonia in aquarium. Ammonia is the by-product of various source, example waste excreted from fishes, organic debris decomposed or waste from aquatic plants. Once ammonia presence even in small amount, the whole process will start. 3 stages involved in whole nitrogen cycle process where nitrifying bacteria will convert ammonia to less harmful nitrites and eventually to nitrates.

Stage 1

The first stage of nitrogen cycle is ammonia accumulation. When aquatic plant and fishes started to be introduced into newly setup aquarium, all the waste excreted will be converted into un-ionized ammonia and ionized ammonium. Accumulation of ammonia will cause the pH of water to be increase above 7. To know whether the nitrogen cycle started or not, you can test the water pH starting day 3 and reconfirm the pH level at day 7. An increase in pH is indicating good accumulation process.

Stage 2

At this stage, nitrosomonas bacteria existed in the aquarium will start to oxidize all the ammonia. Ammonia oxidization will convert ammonia into nitrites which is still toxic to fishes. This normally occur after first week of nitrogen cycle.

Stage 3

The last stage of nitrogen cycle is conversion of nitrites into nitrates. This conversion is being done by nitrobactor bacteria in the aquarium. Although nitrates will be used as fertilizer for aquatic plant, it is best to monitor the level of nitrates in the aquarium as high level of nitrates will be harmful to fishes. Nevertheless, sufficient aquatic plant with partial exchange of water will ensure safe level of nitrates in the aquarium, thus ensuring the aquarium ecosystem is well maintained.

Method for fishless nitrogen cycle

The common way of achieving the nitrogen cycle in newly setup aquarium is by slowly introducing live fish to the aquarium. That natural process normally will take up around 1-1.5 months long. For me, this waiting process is something that really distressing, especially when I’m so eager to house all my fishes into the community tank.

Well, let me introduce another way of achieving nitrogen cycle in shorter time, a method called seeding. With this method, nitrifying bacteria is directly introduced into newly setup aquarium immediately in colony rather that let it being grown slowly. Several methods can be used to achieve the seeding effect and the best part is all these methods can be mixed together to enhance the effect. The first method is by transferring some bio-material from a well established aquarium, either from your others aquarium or from your friends aquarium. The most common place to get the bio-material is from filter, extract some of it and put it inside a mesh.

Another way is by transferring live rock or sand or even plants from well established aquarium and mixed with new one. Some dealer may sell such items, but cautions need to be taken as there is no way to know the source is free of other harmful bacteria. Make sure that if you plan to buy from dealer, be sure that it is from reputable dealer.

I had also come across some aquarist directly transfer the current used filter to newly setup aquarium and let it operates. In certain circumstances, due to well maintenance of the mature aquarium, the level of nitrifying bacteria may not be sufficient enough, causing the whole seeding process fail.It is advisable to test the aquarium after one to two weeks to understand the status of nitrogen level in the aquarium.

Nowadays, shop dealer also sell booster product containing colonies of nitrifying bacteria eg Cycle etc to be added directly into newly setup aquarium. This will definitely give a jump start to nitrogen cycle, but need to fork out with small amount of money. Be careful when using booster as different booster will have different impact. Read the instruction prior to using the booster.


Regardless of which fishless nitrogen cycle methods to be chosen and how short the nitrogen cycle will be, it will still boiled down to how good is the setup. For more information, please find at

Which method of fishless is more effective for you?

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    • henrygogoals profile image

      henrygogoals 6 years ago from Singapare


    • calvincho profile image

      calvincho 6 years ago from George Town

      Good Sharing

    • bjtutu profile image

      bjtutu 6 years ago from Malaysia

      Active dragon, you are correct that commecially available nitrifying backteria is faster. But one caution, make sure the source is from reputable one as some commercially available nitrifying bacteria contained some harmful bacteria.

    • profile image

      brian 6 years ago

      i always thought that nitrogen cycle is only by introducing fish slowly. Dealer never told me that I'm able to use other ways. Thanks for sharing

    • activedragon profile image

      activedragon 6 years ago

      I will usually use the commercially available nitrifying bacteria as it is faster. But have to remember to switch off the UV filter.

      Good and useful article. Thanks for sharing.

    • bihyeong profile image

      bihyeong 6 years ago

      A new learning to me