The optimal dose of ammonia for fishless cycle has not been scientifically studied, that I know of. Since many have chosen an ammonia level of 5 ppm
and had success, it has become more of a tradition than established fact. It is presumed that there is a level at which bacteria will multiply the fastest, below which they will multiply slower and above which they multiply slower. What that level's value is, is just a guess. Low levels, even below the kits detection limit of 0.25 ppm
will establish a bacterial colony, it takes about 7 weeks at 78 degrees, pH of 7.6. (I know this, because I have done it twice). There is a hope that a level of 2ppm would be faster, and a level of 5 ppm
would be faster yet, but a fear that a level above 5ppm would be slower.
Regardless, once you start to see nitrite levels, it is safe to assume that you have a good start to your nitrosomas colony, and they will no longer need high levels of ammonia to continue to grow. I would add no more ammonia until the level goes to zero, then administer 0.5 to 1 ppm
per day thereafter. I suggest this because if you maintain a high ammonia level, all of that ammonia will end up converted to nitrite, and the nitrobacter bacteria are slower growing than the nitrosomas. Thus, to continue to pump high levels of ammonia into the tank will create a large nitrite hump that will take longer for the nitrobacter to catch up with.
Somehow the mathemetician in me feels that the optimal (fastest) bio-filter growth recipe would be an initially high level of ammonia (1 to 5 ppm
) followed by smaller ammonia doses (0.25 to 1ppm per day) once the ammonia has gone to zero. I have actually set up identical tanks to test this "dose response" theory, but somehow life always gets in the way and makes me stop the experiment before it is finished. This is truly an area where the home aquarium hobbyist could actually develope knowledge that the industry scientists have not already done. I just might have to try again.