If you test your top aerobic zones are the levels the same now? No trending needed, I was genuinely interested in knowing.
The test cover 3 months - I think that the time span is large enough to claim that I have the same situation today. Have nor done measurements after 2024-08-14 though
what's the common man going to encounter as far as unused free ammonia, among sandbed bacteria with oxygen present? I cannot imagine such a valuable resource left unused in that proximity to hungry microbes.
In a mature aquarium - sand and stones are mostly occupied by
heterotrophic bacteria - aerobic at the surface and anaerobic in the deeper layer of sand, deeper pockets of rock and if the rock´s biofilm is thick enough - the deeper part of it. If
autotrophic nitrification bacteria is present - they are in the upper layer of a thin biofilm.
The
heterotrophic bacteria is mostly "break down" bacteria - they breaks down organic matter in a process named mineralization - it means - organic carbon -> mostly into CO2; organic phosphorous -> dissolved PO4 and organic nitrogen into NH3/NH4. Of the organic matter existing at a certain time stamp - around 20 % will be built in into bacteria biomass - around 80 % will be mineralised. This breakdown process is much, much faster in an aerobic environment compared with an anaerobic environment.
Contrary to popular belief, bacterial decomposition in most cases results in the formation of CO2, PO4 and NH3/NH4 from organic carbon, organic phosphate and organic nitrogen. Up to about 80% of the organic "elements" will be mineralized in this way.
In most cases this process is accelerated by access to "fast" organic carbon (labile DOC)
My experiment showed that this happens quickly because in the plenum 6-8 times more NH3/NH4 was continuously "dissolved" than was present in the incoming water. Important to know is that there is only around 1-2 L below my plenum and the flow through this volume was - at the relevant time period - between 60 and 80 L per hour.
It can be mentioned that PO4 shows a significantly more complicated picture - sometimes it was dissolved - sometimes it was taken up. The same applies to NO3 while NO2 shows a strong tendency to be released below the plenum
The redox potential indicates that there is a preponderance of oxidation below the plenum - thus the processes below the plenum are likely aerobic.
All of this together supports the assumption that a sudden increase in degradable organic matter - such as a dead fish - increases the risk of NH3/NH4 release and accumulation in the water column.
Also, since I too linked a valid thread earlier showing copious ammonia dosing into seneye tanks, you can see many of those are prime value examples showing consistency down to thousandths ppm and you can see how many different reefs attain that average, after calibration.
Once again - Seneye only shows the NH3 part of NH3/NH4 and it is only around 5-10% of the total NH3/NH4 concentration. It is not suitable, accurate enough or fast enough to be used for this type of measurements. API gives an indication but for hobby use Hanna's method for measuring NH3/NH4 is superior - at least with the Hanna Marin Master that I have used.
Sorry for the long post but I want to try to show - once and for all - that all the talk about high NH3/NH4 concentrations not being able to occur in an old and mature aquarium is nothing more than the bull's leftover after it has eat.
Sincerely Lasse