i’ve seen a discussion between marine biologists on nutrition, they mention that it is expected to be a lost of around 90 percentile between tropic levels.
Warm-blooded animals have mostly 90% loss - cold-blooded animals like fish is normal said to have 80 % loss compared with the energy and nutrition on food they eat. For heterotrophic bacteria - I do not know but the loss is probably around these figures.
1. How can I reduce organics in the water without also removing some trace elements?
2. How can I reduce nitrate in the water without also removing some trace elements?
3. How can I reduce phosphate in the water without also removing some trace elements?
I think it is very important to distinguish between trace elements (yes all elements for that matter) in the water column and in dead organic matter. If you look at the whole system (water column + dead organic matter) there is no export method that does not involve loss either chemically bound or bound in new biomass - IMO. Even if denitrification is very species-specific and most of the inorganic N will leave the whole system while everything else remains in the system
If we instead concentrate on trace elements in the water column - the ones we can measure - I am quite convinced that 1 and 2 are feasible and also with methods that provide the system with new trace elements and other inorganic substances
1) Organics in the water - both dissolved and as particulate organic matter can be expressed as BODx there BOD stands for Biological Oxygen Demand and x for the actual days the test is run. The microbes "eat" the organic matter - transform around 20 % to its own biomass and release the other 80 % as inorganic substances - most as dissolved inorganic - including inorganic P, N, C and most of the other substance that is Incorporated in organic matter. All of this happens fast when Oxygen is present. A filter of some type with a fast flow of oxygen rich water will speed up this process and also release inorganic substances into the water. But 20 % of the original organic matter is transformed into new bacterial biomass and can be exported out from the system with help of rinsing the filter.
However - its not valid for all traces and pollutants. Some of them are toxic to many bacteria and therefore the bacteria must be able to transform these into - for them - harmless products - usually this means making them fat-soluble and therefore bio-accumulate them into the biomass in fat depots. Mercury is one such pollutant that bio-accumulates, as are copper and cadmium.
For example, metallic mercury is toxic to most bacteria - they then convert it into methylmercury which is not toxic for them and can be stored in the biomass or bind into humus.
This method is a rather slow export method but can be done with a biological filter that is rinsed now and than - it takes away maybe 20% of the traces from the organic matter but on the other hand it also release new traces into the aquarium from the organic leftover in the tank.
The bottom line is that microbiological decomposition (mineralization) does not take many substances from the water - instead, the process adds substances to the water from the decomposed organic material.
2) NO3 can be removed from the water with classic denitrification. In this case - most of the NO3 is not used as a "normal" nutrient that will be Incorporated in bacterial biomass - instead will it replaces the oxygen in the bacterial cell's metabolism (combustion)
The bottom line is that classical denitrification is species-specific and removes only NO3 from both the water and the entire system - in that process nothing else is removed. Some substances are incorporated into the biomass of the bacteria that carry out the denitrification, but are a negligible proportion in relation to the amount of NO3 that is removed.
In this case, very little inorganic material will be bound in bacterial biomass as organic matter because the process is slow and inefficient. As for the biomass, it follows the usual rule - around 20% bacterial biomass. 80% as dissolved inorganics in the water column.
3) P does not have a gaseous phase like N does. Therefore, I believe that PO4 follows the same rules that I try to explain in point 1.
My 20% biomass and 80% dissolved inorganic should be taken with a pinch of salt. Some organic substances are difficult to break down and then remain as difficult to break down DOC in the water - we usually call them yellow substances but the common name is humus.
Sincerely Lasse