Before you can start stocking a new tank you need to cycle it, and this doesn't involve riding a bike! Traditionally this was carried out using fish as a source of ammonia to feed the filter bacteria. However fishkeepers know that the toxins produced during cycling are harmful to fish, this has led to more fishkeepers embracing a far more effective and safer form of cycling, called fishless cycling.

Instead of using fish, fishkeepers use other sources of ammonia to feed the bacteria, the most popular are fish food and bottled household ammonia (which is usually available from chemists). The bacteria begin to colonise the filter media (either in the form of a sponge or ceramic balls or rings) and start to break down the ammonia into less harmful substances. The end products are removed by water changes and aquatic plants, the whole process is called the nitrogen cycle, and it is explained in more detail below.

The cycling process and the nitrogen cycle.





As you can see from diagram 1, ammonia starts to peak within a few days (possibly a week) of being added to the aquarium. After a couple of weeks the ammonia starts to drop and another harmful toxin is produced, called nitrite. Over the next couple of weeks the nitrite will drop, but another substance, this time less harmful, called nitrate is produced. At the end of the cycle the nitrate starts to peak and nitrogen gas and phosphate are formed, at this point you should carry out a partial water change to remove built up nitrates. Diagram 2 shows the whole process of the nitrogen cycle within an aquarium.

Another method of cycling a new tank is called seeding, which involves taking mature filter media from one filter and placing it inside another to cycle the tank. The cycling process is effectively cut short by doing this, but you should still wait for a couple of weeks to allow the tank to mature.

Whatever form of cycling you use in your aquarium, remember to stock slowly, adding no more than a few fish every few weeks.

Whilst I completely agree with the concept and principles of the cycling, I'm just wondering how high you believe your nitrite gets - it is shown to peak at 50 ppm, which is very high to me. I doubt that the hardiest of hardy fish survive that, seeing as 0.5ppm is considered VERY HIGH under normal circumstances (and I'm by no means saying that it can'0t go well above that, this article seems to indicate that 6-8 ppm of nitrite or ammonia is sufficiently high that the cycling process is harmed by it, if I read that part correctly, about one and a half page down from the top). I think you are off by a factor of 10 or so on the nitrite and ammonia scale.

And I wish I could have as low nitrate as you indicate - even my tap-water is more than 20 ppm (and the water company agrees, I asked for their water quality report, and if memory serves, it was 37 ppm average over the year, with a low of about 30 and a max of nearly 50). RO unit takes care of that for my softwater fishes. Hard-water fishes get large and frequent water changes [one of my setups started with two tanks, now three and soon to be four, that get my RO water waste-water, which is essentially replacing the water a couple of times a day for the entire water-volume, through a sump-filter and overflow system].

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Mats

Whoops, the diagram wasn't designed by me but I'll try and find a more precise one.

The article is just a general guide however all constructive criticism is welcome.

I've changed the diagram to one that doesn't show the amount of ammonia and nitrite produced during the cycle, just the general timescale of when it rises and falls.

Yeah, that's much better.

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Mats