No, Mama, that is not the way it really goes. There is a little math and chemistry involved and then the nature of our test kits. Understanding, these will help to clarify this situation.
Given the atomic weights of NH3/4, N02 and NO3 and the fact that out test kits measure total ions: 1.0 ppm NH3/4 becomes 2.6 ppm of nitrite which becomes 3.5 ppm nitrate (I rounded here).
So, if one puts 3 ppm of ammonia into a tank it will eventually create a total of about 7.8 ppm of nitrite. So what happens after that 3 ppm goes into a tank.? The bacteria that convert it to nitrite start to multiply. The are converting some small amount of ammonia almost right away and multiplying as fast as they can in response to all that good excess food being available. So lets wait a few days or a week and test ammonia again. For the sake of this discussion lets say the ammonia dropped from 3 ppm to 2 ppm. Where did that 1 ppm go? It became nitrite.
The process of converting ammonia and nitrite is not instant. The Abacs don't have a storage facility for nitrite so they can wait to release it all at once. In goes ammonia and out comes nitrite. And for that 3 ppm of ammonia to be mostly gone, it means about 7.8 ppm of nitrite were created.
My point in my post above is that what stalls the cycle in most cases is high nitrite. It is rare that folks overdose ammonia to the point of stalling things, the test kit catches this. If one accepts that high nitrite is the culprit in many cases, then they should agree it was ammonia which produced it. That is why, when fishless cycling, you need to see more than the ammonia drop before you dose again.
Lets assume for a minute we see that 3 ppm of ammonia is down to about .25 ppm. One should have nitrite in the several ppm range because there are nowhere near enough N-bacs to handle things yet. If one doses another 3 ppm of ammonia here what happens next? Since there are now a decent colony of A-bacs built up, they go to work on the new ammonia and pretty quickly its almost gone and there are another 7.8 ppm of nitrite created to be handled handled on top of most of what nitrite was already there when the second ammonia dose was added. So now the nitrite can be approaching a number as high as even 12-15 ppm on the API kit. But this kit won't measure that, so the odds are good one has no idea of where nitrite levels are.
If you have watched the vid I like to link showing of Dr. Hovanec testing for nitrite using an API, Nutrfin and lab grade Hach test kit, you know that the first two kits can and do read 0 or low nitrite in the presence of actual high nitrite levels well above the scales on the hobby test kits.
For that reason seeing ammonia drop to almost 0 is not a reason in and of itself to add more. One needs to know that nitrite levels are low enough not to be a problem.
There really are only two effective methods for doing a normal fishless cycle. I say normal because there are situations re cycling where is it possible and advisable to be dosing way more ammonia than is usually suggested. But those are the exceptions not the rule especialy for folks new to the hobby.
Dose and test involves adding "higher" amounts of ammonia all at once several times during tre cycling process. The dose and test term came from the days before ammonia calcs etc, and because of the variability in the strength of different ammonia sources. So you dosed and tested until you reached the desired ppms. Testing itself is done during cycling to know where things stand at any given time no matter what method is used.
Daily dosing is a method no longer used very often which involved adding much lower amounts of ammonia every day. This method is actually more similar in how the numbers produced compare to a fish in cycle. This was the original methodology for fishless cycling before the dose and test came along. I did about 65 tanks this way.
The thing about both of these methods is they should be done in such a way as to prevent the undesirable buildup of ammonia or nitrite which can stall a cycle.
Unfortunately, over the years from the urban myth system on fish sites the methods got all get mixed up and suddenly there is a method of dosing daily to get back up to a level somewhere between 3 and 5 ppm.The problem is there are not many fishless cycling situations where there this method wont spell doom.
One way to understand the difference between the fishless vs the fish in cycles in terms of how the ammonia, nitrite and nitrate behave is in how they would look on a chart. here is the traditional graph for fish in:
In fishless the nitrite curve looks basically the same as above, but the ammonia curve is totally different. In the chart above the ammonia curve starts at 0 peaks and drops to 0. Note- the nitrite appears before the ammonia even tops.
But in a fishless cycle that ammonia curve looks way different. It starts at 3, makes a curving dip close to 0 and then suddenly spikes straight up to 3 again and then drops in a curve towards 0, only much faster than the first time. Then you add ammonia again and up it spikes to 3 and drops even faster than the last time. The nitrite curve, though it will have a somewhat similar shape, will top out at a much lower ppm reading than during a fish in cycle. (Please note that chart ppms are in -n readings, not total ions)
For the person just getting into fish keeping the process of cycling should be as simple and straight forward as possible, It should be designed to minimize the potential for having things go wrong. Over dose 3 ppm of ammonia by 1/3 and its 4 ppm. Do the same with a 5 ppm dose and its 6.65 ppm (API kits) and that is enough ammonia to stall the cycle. Make a mistake in the opposite direction and under dosing by 1/3 means you are at 2 ppm and the tank will still cycle.
Nor do I understand the concept of having to reach 0/0 in 24 hours for multiple days in a row to know one's cycle is done. Either a tank can do it or it can't. If you are concerned your test kits might be wrong, no number of times will fix that. If you are a super cautious person maybe do it twice. But there is no reason I can imaging for doing it for a week (either 5 or 7 days).
One can shorten the period involved if you also reduce the dose involved. On the surface 12 hours and 1/2 the dose sounds good, but it isn't quite that simple. A tank normally produces more ammonia during the day when everything is more active. Waiting 24 hours using a full dose is more reliable because it encompasses a complete light and dark cycle. I would suggest if one wants to be safest using a 12 hour test done during the day that about 60% of the full dose would be more appropriate.
I hope this helped to clarify things.
Remember, the way to cycle faster is to pedal harder........
