Well, I would put it a different way, its not cheating at all. Your tank is already cycled more or less, whats happening now is we're being sure the if you were to put a full stocking (pushing the one inch of fish body per US gallon right up to the number of gallons you have) in there immediately after the big water change, that the filter would be stable and would not "mini-cycle" on you. Its very common though for people to find, once they are near the end of their stocking plan, that they have one or more species that they are going to "wait on." Very commonly this might be a big shoal of cardinal/neon tetras (since you need to wait 6 months on those) or it might be a pair of "centerpiece" fish because they are expensive (or sensitive, like GBRs for instance) and you want to further stabilize the tank beyond just the cycling part. So if there are a significant number of fish "delayed" from the initial stocking and you are going to come in significantly below the one inch guideline level of stocking, then its often perfectly ok to skip the "final sticking episode" and go ahead with the big water change and the partial stocking introduction. (We're assuming probably no more than a 75% bioload introduction if that makes sense?)
What happens at the big water change and initial introduction is that you want the colonies of the two species of bacteria to be capable of handling a much larger bioload than you introduce. This allows them to drop back down and perfectly match whatever bioload you put in. You always want this because its impossible to perfectly match a colony set to a given bioload and it certainly doesn't work to place more bioload in with undersized colonies because then you're just back to a fish-in cycle.
The 12 hour drop point has been talked about and respected for a long time I believe but I know it came about in earnest here in the TFF beginner section over a years time and was discussed a lot by me, Miss Wiggle and BTT, who were quite actively helping at the time. What had become quite obvious was that a lot of people were getting to where ammonia and nitrite was dropping to zero somewhere between 12 and 24 hours or perhaps they reached their very first instance of double-zeros (as that's called) at 12 hours and they would jump for joy and get fish. Then quite a few of them would experience are rather sharp mini-cycle and end up changing a lot of water for a week, despite having "done a fishless cycle." What we worked out was that if ensured that the toxins were clearing in 12 hours and then performed a "qualifying week," watching it do that for about a week (or the rest of a week until they could buy fish on a weekend was the idea) then we found we had almost a 100% success rate with members who were willing to do that for their case. The efficacy of it seemed to be reinforced because a significant number of people did indeed find thay they had surprise spikes during that qualification week. But then once they finally had a successful qualification week they virtually never saw spikes after that (assuming a decent filter of course!)
Anyway, I know you are in pain now and I feel for you. I had a fishless cycle that ended up totaling 160 days (because a tank broke in the middle) and martinking and some others have had ones over 100 days. But most of the very long ones are no longer than between days 60 and 70 and many, many cycles are less than that, leading us to cite 3 weeks to two months as a reasonable average, which I still feel is reasonably accruate.
~~waterdrop~~
