OldMan happy to see you are coming around to the lower dosing method. The next step is to reduce the max levels from 5 to 4 ppm. The reason for this is simple, it gives a margin of error. New fish keepers may make mistakes in testing or dosing. If one doses too little, it wont hurt anything but it may make the cycle take a tad longer. Overdosing in excess of 5 ppm will usually have worse consequences.
The idea to dose to 4 or 5 ppm and even higher originated with the early fishless cyclers. However, they also advocated using as much seed material as possible. When you can jump start with a lot of bacteria it changes the paradigm relative to how much ammonia one can dose safely. But even back then they had an inkling that going too high with ammonia and/or nitrite was likely bad. They just did not know why for sure. The why is it can inhibit the bacteria or even kill them.
My experience with daily dosing has been it only works well when the daily dose is pretty low (higher works if the level of seeding is high). This way ammonia never builds to substantial levels before ammonia oxidizers start to work and it also helps hold down nitrite levels until the nitrite oxidizers appear. Best estimates are I started at about .50 ppm/day until nitrites appeared when I reduced it to about .35 ppm/day until fully cycled.
white_and_nerdy- the reason is that the amount of ammonia most established and stocked tanks will produce is pretty low. Remember, it is not all produced in a single big load the way dosing ammonia does. In an established tank ammonia is being produced 24/7. While the actual rate will vary with different times of the day, it is still basically a low level ongoing process. Therefore, the amount of bacteria needed isn't what can handle a single big dose quickly, but what can process the much lower level ongoing amounts. Which is why almost any fishless cycling article you will read tends to agree on one thing. You are cycled when you can dose X ammonia and then test in somewhere between 12 and 24 hours and get a 0 reading for both ammonia and nitrite while showing increased nitrate levels over the same period. The time is needed because the amount of ammonia that one's tank might naturally produce over that 12 or 24 hours would add up to somewhere closer to the X amount.
Think of it this way, 2 ppm in a day, if it were uniformly produced, is only .083 ppm/hour. 4 ppm a day would be .166 ppm/hour. So what your final dose test really shows is that your tank could handle the ongoing levels in that range.
Daily dosing of the equivalent of 4 or 5 ppm without a huge amount of bacterial seeding is a sure fire path to problems and failures, imo.
