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view/download model file: RevisedNitrificationmodel.nlogo
This model demonstrates how the nitrogen cycle works in an aquarium. This is part of in important biogeochemical cycle.
As a fish is placed in a tank, the produce ammonia and bacteria are recruited from air. These bacteria use nitrogen compounds, ammonia or nitrite, for energ. One bacteria uses enzymes to convert ammonia to nitrite. ;bacteria needs to appear randomly in patches once ammonia, nitrate reaches a certain level ; nitrosomonas (the cyan patches) appears before nitrobacter ; nitrosomonas reproduces more rapidly than nitrobacter/nitrospira (violet patches) ; each bacteria needs some level of nitrogen compound to reproduce ; nitrosomonas converts NH4+ to NO2- with some probability ; nitrobacter converts NO2- to NO3- with a smaller probability than above ; to prevent overpopulation, bacteria have limited life span ; molecules are converted on contact with bacteria (probabilistically noted above)-- move randomly around tank ; plants take up nitrate so if there are many plants, the nitrate levels will be lower ; nitrates also removed through regular water changes
Set the number of fish at 1 and number of plants as desired.
The red circles are ammonia, the white circles are nitrite, the yellow circles are nitrates. The cyan patches are nitrosomonas, the violet patches are nitrbacter/nitrospira. Notice the sequence of the tank cycling.
See what happens if you add more fish, more or less plants. Look at the effects of regular water changes
Decomposition of solid waste, uneaten food and plants creates ammonia. The Nitroren cycle uses dissolved oxygen-- this would be an interesting extension of the model. Seeding the model with gravel from an established tank.
This section could point out any especially interesting or unusual features of NetLogo that the model makes use of, particularly in the Procedures tab. It might also point out places where workarounds were needed because of missing features.
Created by Cindy Hmelo-Silver July 2005