Ammonia And Beneficial Bacteria

[celaeno]

will too much ammonia in the tank kill off some of the beneficial bacteria in the filter? i'm asking to compare the two main fishless cycling methods - add daily, and add and wait.

 

[Bignose]

It isn't so much that high amounts of ammonia kill off the bacteria, but it is that high levels of ammonia stimulate the growth of a different kind of bacteria. This information has only been discovered recently. This is why all the aquarium literature before the late 1990's -- and for that matter quite a lot still today -- identify the species name of the cycling bacteria wrong. It was assumed that all ammonia oxidizing bacteria (AOB) were all the same, or at least very, very similar. So, when the species of bacteria in wastewater facilities was identified, it was just assumed that those were the same AOB. It wasn't until the research of Dr. Tim Hovanec that the actual species common to aquaria were identified. It turns out that is kind of explained the apparent "stall" of filters when the ammonia level got too high. The ammonia levels when they get too high, don't so much prevent the growth of the aquarium species, but spur the growth of the wastewater AOB. And, just like it takes time to grow up the aquaria AOB, it take time to grow up the wastewater AOB. So, there appears like there is a stall.

In a roundabout way, the answer actually is yes, because you don't really want the wastewater AOB in your tank -- they'll die off if there aren't high levels of ammonia and then the aquaria AOB will have to grow back up anyway. So, you don't want to be increasing the ammonia level super high.

But, the usual recommendations for fishless cycling is to add ammonia each day to bring the total concentration up to around 5 ppm. Obviously, the first week or so, the amount of ammonia the AOB are going to consume is going to be really small, so you don't have to add anything that first week or so. But, eventually, you're going to have to add to bring it up each day.