It is quite simple Gamwar.
Ammonia in a tank is converted to nitrites by bacteria. Nitrites in turn are converted to nitrates. The ratios involved are 1 ppm of ammonia becomes 2.7 ppm of nitrites which becomes 3.6 ppm of nitrates. Since there is more at work here than simple bacterial conversion, sometimes the observed results do not add up. That means you must instead treat these numbers as a general idea of what to expect to happen instead of trying to do calculations and expect them to work out exactly.
A fishless cycle is a simple concept. We add some ammonia to the tank water and watch for both the ammonia conversion and the nitrite conversion to happen. In real world terms, the water in your water supply probably contains a small number of both bacteria. We grow that small population in our tanks by using ammonia in low concentrations, high concentrations encourages the wrong bacteria to develop. Instead of using high concentrations of ammonia, we use numbers of 2 to 5 ppm of ammonia. That means we are encouraging the right bacteria to grow in our filters. In concentrations of as little as 8 ppm ammonia, it has been shown that the wrong bacteria will dominate the bacterial population.
OK so what happens from here? We try very hard to not encourage the wrong bacteria by always letting the ammonia levels get close to zero before we dose back up to only 4 or 5 ppm. That means we never cross the line and encourage the wrong bacteria to grow. By doing things that way, the typical 24 hours or so doubling time for A-bacs, ammonia processing bacteria, is allowed to produce the needed A-bac population as a film on your filter media.
The next step is just as important. Lets not forget the huge ppm increase that happened between ammonia concentration and nitrite concentration. You are now working with very large populations of nitrite processing bacteria, N-bacs. Since we again only have thew traces of N-bacs we got from the raw tap water, the time required to grow thew N-bacs is often even larger than the time needed to establish the A-bacs. WD and I have speculated that the N-bacs may have the same problem developing properly in high concentration situations that the A-bacs are known to have. For that reason, we will often suggest that someone not seeing a good response of N-bacs and subsequent reduction in nitrites might benefit from reducing the nitrite levels to a value that can be read using your teat kit. I have no idea whether or not this particular advice is a plus for your cycle but I know it cannot hurt and it may help if our speculation that a similar relationship may exist is right.
To summarize, I find that I can picture a lump of ammonia in my mind being processed through the nitrite phase and on into the nitrate phase. That lump of ammonia is a real and living thing to me and means that I can visualize ir and suggest what would be best to deal with it.
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