Not sure if this will help clarify for some but...
bacteria consume the ammonia as a food source which is expelled as nitrite (all bacteria expell nitrite to a degree). The next stage is nitrobacters
which consume the nitrite and expell it primarily as nitrate. That is the extent of nitrification.
The next stage is denitrification and what completes the nitrogen cycle. This is accomplished by varying sets of bacteria. Primarily strict (or obligate) anaerobes (less desirable) and facultative anaerobes (more desirable). Strict anaerobes live within an oxygen void environment and consume honorary oxygens or elements containing O2
. Anaerobic biproducts
are quite nasty resulting in partly methane and hydrogen sulphide.
Facultative anaerobes live within an oxygen reduced environment refered to as anoxic. They can alter between an O2
void environment, as with the areas within LR
or a shallow sandbed. The larger the rock the more likely the denitrification process to work depending on porosity. Facultative bacteria IMO
being the more desirable in an anoxic setting due to the final stages of their waste expulsion being CO2
and nitrogen gas. If these same bacteria end up in an oxygen void environment they switch to a fermentation
style of digestion.