I am not sure how you would like me to present proof of this when it is something that happens in our aquaria, not on paper. If you are looking for data on the biological processes that are involved in a cycle, that data is available all over the net. I will, however, provide a short excerpt here that explains why an "overnight cycle" is impossible:
"Nitrifying bacteria have long generation times due to the low energy yield from their oxidation reactions. Since little energy is produced from these reactions they have evolved to become extremely efficient at converting ammonia and nitrite. Scientific studies have shown that Nitrosomonas bacterium are so efficient that a single cell can convert ammonia at a rate that would require up to one million heterotrophs to accomplish. Most of their energy production (80%) is devoted to fixing CO2 via the Calvin cycle and little energy remains for growth and reproduction. As a consequence, they have a very slow reproductive rate.
Nitrifying bacteria reproduce by binary division. Under optimal conditions, Nitrosomonas may double every 7 hours and Nitrobacter every 13 hours. More realistically, they will double every 15-20 hours. This is an extremely long time considering that heterotrophic bacteria can double in as short a time as 20 minutes. In the time that it takes a single Nitrosomonas cell to double in population, a single E. Coli bacterium would have produced a population exceeding 35 trillion cells."
When a tank is showing non-detectable levels of ammonia and nitrite it is because the populations of nitrifying bacteria are at an equillibrium with the current output of ammonia into the system. In order to have a deadly spike of ammonia you first need a source, i.e. dead fish, heavy, heavy overfeeding or a loss of nitrifying bacteria. For sake of argument, even though it would be very, very improbable, we will say that when he tested the water on the morning before the "spike" it was at zero and then by that night it shot up to 1 or 2ppm. Let's also say, for example, that the bacteria were multiplying at the optimal rate to try to meet the food source. It would still take at least 7 hours for them to double in numbers and the increase of ammonia concentration is far greater than double. Even still, we will pretend that the Nitrosomonas have converted all of the ammonia overnight. You are still left with the Nitrobacter having to pick up on the presence of nitrite and catch up with those rising levels. At the very least, that would be detectable on tests. Here is a link for the above information:
http://www.bioconlabs.com/nitribactfacts.html
I have also been maintaining aquaria, both fresh and marine, since the mid eighties so am not a newcomer either. I do not simply parrot what others say on this forum as sometimes they are simply wrong or guessing themselves. If your aquaria take a full year to establish a healthy bacterial load and have multiple cycles during that time period then there is something not quite right. Detectable waste levels occur when excessive waste is put into the system or the mechanisms to remove it are debilitated. Both of those things should be fairly easy to determine the source of and control. Having a full understanding of the biological processes that exist in our tanks makes it much easier to troubleshoot issues without error. Happy reefing.
