Congrats Chrissi on your accomplishment!
I expect you or your boyfriend are going to be seeing lots of lemon yellow and sky blue at those 12 hour tests pretty soon and probably on and on after this.
Gosh, I'd love to talk you in to considering an initial stocking of a cory shoal and the Honey gourami! Both of those would probably be happy as clams in this nicely cycled new tank! Then you could watch them closely and get used to their habits and really be a good fishkeeper to them, all the while letting your chemsitry do its thing and mature a bit longer for your shrimp and finally your tetras.
Its really, really hard in situations with little tanks where the neons/cardinals are planned to be the main show. The fishless cycler has already sacrificed so much to get the good filter going and then the thought of waiting yet longer and for no really specifice reason seeming to be given...
Let me just try to convince you though. A water environment is a much, much more complicated system than our simple discussions here would indicate. Out of practicality we as hobbyists pass around information that greatly simplifies the picture. I'm sure you've thought about how those main substances you've been dealing with for the recent months could be graphed and you would see different curve lines for each over time during the fishless cycle (some past members have even -posted- very nice web available graphs of their cycles.) Well, the NH3 would sit there at 5ppm for days and then finally begin tapering down and the it would begin jumping up to 5 where you added and quickly dropping down to zero day after day. The nitrite peak would come much later than the ammona and would rise slowly and then remain peaked during the nitrite spike and then would finally begin going regularly up and down like the ammonia. The pH would start somewhere and gradually taper down as the nitric acids made things more acid and the nitriates would just be gradually going up and up and up perhaps until a water change. All these different graphs...
Well these are just 4 (!) things, right? The tank environment actually has hundreds of these! We are just not measuring and graphing them. (Ha,Ha, think of one of those fancy computer monitors over the patients bed on one of those television medical dramas where lots and lots of graph lines are scrolling by in different colors, then the heartbeat stops and everyone stares at the graphs for a moment in horror!

)
For instance.. Once we start learning about plants, we realize there are about 17 or 18 or so essential elements that are nutrients for them and you could have the 17 graphs individually going up and down all in different ways as the days and weeks roll by. (Carbon, Oxygen, Nitrogen, Hydrogen, Potassium, Phosphorus, Calcium, Magnesium, Iron, Sulfer, Silicon, Chlorine, Boron, Manganese, Sodium, Copper, Zinc, Nickel, Molybdenum... well you get that picture) ... and YES, they're really in there, right in your tank!
But that only -starts off- things because of course there are all sorts of organic and inorganic compounds being formed and broken down USING these many elements. For instance, one important group gets the tag "Dissolved Organic Carbons" or "DOC" for short. DOC is a thing that can slowly build in a tank and do all sorts of wonderful positive things! Anyway, down in this molecular world of the tank you can begin to imagine that there are all sorts of elements and compounds that are either "there" or "not there" at different times and different ones matter or don't matter to different degrees. Astoundingly complex if one could "see" down in there.
But Wait! There's More! as they say on the late-night tv ads, lol. There are... critters

, yup, remember them? There are all these other bacteria species besides the 2 we've been thinking about. There are fungi. There are algae. Each of these things is mind-bogglingly complex on its own! There are micro-biologists out there stuggling daily to work out 3-dimensional pictures of individual molecules in these things!
All that's to say that no, we don't have a handle on it scientifically at all really. Now switching completely to a different thing, total subjectivity, my own observation a number of times with tanks is that there's a time that comes, about 6 months out, when the tank just seems to "reach perfection" somehow. There's a change that somehow seems to be a coming together of a lot of things and the water somehow seems more clear, the color seems somehow different.. I don't know how else to describe it but I've heard other aquarists express similar things. Anyway, its my hunch that this subjective point is somehow related to something that the neons/cardinals find to be perfect too.. somehow.
I know, I know, now you will just get even more of a kick out of introducing them after the fishless cycle and getting to tell me you didn't lose a single one!

sigh...
~~waterdrop~~
