The important thing to keep in mind is that depending upon the pH and temperature, the AOB and NOB (ammonia oxidizing bacteria and nitrite oxidizing bacteria) will appear and establish a colony in any aquarium, with or without plants. In water with a pH below 6 the bacteria cannot live, so this is a non-starter; temperature also has a similar effect though I cannot remember the actual number, but no matter because we would not/cannot maintain tropical fish at such temperatures anyway so that is a non-starter. But in water that is less acidic and more up in the basic pH, the AOB and NOB will establish, regardless of plants. So the "bed" is there, so to speak.
That is the critical issue. It is the initial establishment of the AOB/NOB that takes the two to eight weeks. Once they are established, they will multiply according to their food source. The plants will take up most of the ammonia, but I have never read where they will take it all up, so some sneaks by as @seangee I think mentioned above. The bacteria bed establishes. Should something occur to increase the ammonia beyond what the plants can take up (the plants die for example) the AOB only need roughly 12 hours to reproduce by binary division. The NOB require longer, up to 30 hours approximately. But this is simultaneous once both species are established. The following excerpts from an article I wrote some years back may help to explain this.
[2] Paul C. Burrell, Carol M. Phalen, and Timothy A. Hovanec, “Identification of Bacteria Responsible for Ammonia Oxidation in Freshwater Aquaria,” Applied and Environmental Microbiology, December 2001, pp. 5791-5800.
[3] Hovanec, T. A., L. T. Taylor, A. Blakis and E. F. DeLong, “Nitrospira- Like Bacteria Associated with Nitrite Oxidation in Freshwater Aquaria,” Applied and Environmental Microbiology, Vol. 64, No. 1, pp. 258-264.
[4] Kim, D.J., D.I. Lee and J. Keller (2006), “Effect of temperature and free ammonia on nitrification and nitrite accumulation in landfill leachate and analysis of its nitrifying bacterial community by FISH,” Bioresource Technology 97(3), pp. 459-468.
[5] Kmuda, “Aquarium Bacteria and Filtration Manifesto,” Parts 1 and 2, OscarFish website.
That is the critical issue. It is the initial establishment of the AOB/NOB that takes the two to eight weeks. Once they are established, they will multiply according to their food source. The plants will take up most of the ammonia, but I have never read where they will take it all up, so some sneaks by as @seangee I think mentioned above. The bacteria bed establishes. Should something occur to increase the ammonia beyond what the plants can take up (the plants die for example) the AOB only need roughly 12 hours to reproduce by binary division. The NOB require longer, up to 30 hours approximately. But this is simultaneous once both species are established. The following excerpts from an article I wrote some years back may help to explain this.
Nitrification is the oxidation of ammonia/ammonium to nitrite and then the subsequent oxidation of nitrite to nitrate; this is performed by two groups of bacteria known collectively as nitrifying bacteria or nitrifiers. True nitrifying bacteria are autotrophs; they use chemosynthesis to manufacture their energy by using oxygen plus nitrogenous waste (ammonia or nitrite) and carbon (from CO2). There are several different bacterium species involved, all in the family Nitrobacteraceae, that carry out this function in soil, and it used to be thought that these, particularly Nitrosomonas europa and Nitrobacter, were the nitrification bacteria in freshwater. But Dr. Timothy Hovanec led the team of scientists that proved this to be a mistaken assumption. Ammonia is converted to nitrite by bacteria of the Nitrosonomas marina-like strain [2] and nitrite is converted to nitrate by bacteria closely related to Nitrospira moscoviensis and Nitrospira marina. [3]
Once established, the population of these bacteria in an aquarium will be in direct proportion to the amount of ammonia or nitrite respectively. Nitrifying bacteria require 12-32 hours to multiply, which they do by binary division [each bacterium divides into two bacteria]. Nitrosomonas multiply in less time (12+ hours) while Nitrospira require more time (up to 32 hours). In a new aquarium, it can take up to eight weeks for the bacteria populations to reach a level capable of eliminating ammonia and nitrite.
The pH has a direct effect on nitrifying bacteria. These bacteria operate at close to 100% effectiveness at a pH of 8.3, and this level of efficiency decreases as the pH lowers. At pH 7.0 efficiency is only 50%, at 6.5 only 30%, and at 6.0 only 10%. Below 6.0 the bacteria enter a state of dormancy and cease functioning. [5] Fortunately, in acidic water (pH below 7.0) ammonia automatically ionizes into ammonium which is basically harmless. And since nitrite will not be produced when the ammonia-oxidizing bacteria are in “hibernation,” this decrease in their effectiveness poses no immediate danger to the fish and other life forms.
Temperature also affects the rate of growth of nitrifying bacteria. It will be optimal at a temperature between 25 and 30C/77 and 86F. At a temperature of 18C/64F it will be 50%. Above 35C/95F the bacteria have extreme difficulty. At both 0C/32F (freezing) and 100C/212F (boiling) the bacteria die.
These bacteria cannot survive drying out; without water, they die. Tap water with chlorine may kill these bacteria, depending upon the level of chlorine and the duration of time the bacteria are exposed to it. Some antibacterial medications may negatively impact the nitrifying bacteria to varying degrees.
[2] Paul C. Burrell, Carol M. Phalen, and Timothy A. Hovanec, “Identification of Bacteria Responsible for Ammonia Oxidation in Freshwater Aquaria,” Applied and Environmental Microbiology, December 2001, pp. 5791-5800.
[3] Hovanec, T. A., L. T. Taylor, A. Blakis and E. F. DeLong, “Nitrospira- Like Bacteria Associated with Nitrite Oxidation in Freshwater Aquaria,” Applied and Environmental Microbiology, Vol. 64, No. 1, pp. 258-264.
[4] Kim, D.J., D.I. Lee and J. Keller (2006), “Effect of temperature and free ammonia on nitrification and nitrite accumulation in landfill leachate and analysis of its nitrifying bacterial community by FISH,” Bioresource Technology 97(3), pp. 459-468.
[5] Kmuda, “Aquarium Bacteria and Filtration Manifesto,” Parts 1 and 2, OscarFish website.
