Hi all,
Is this NO3 in the same form as our inorganic NO3 salts we add in EI?
Yes.
I know plants produce waste but I can't seem to find what (apart from O2 and CO2).... Have I got carbon compounds floating around?
Yes.
Plants are very "leaky" structures, and some proteins, lipids, hormones and carbohydrates will be leaking out all the time, from leaves and roots. This is particularly true as senescence of damaged leaves occurs.
This is also where the BOD (Biochemical Oxygen Demand) concept comes in really useful. A dead fish or a fed prawn is going to contain a lot of protein, and that protein (via decomposition or excretion of excess nitrogen if they are eaten) will have a very high BOD. The same applies to a fruit like Mango, or a vegetable like Sweet Potato, that you might feed to Loricariid catfish or a Pacu these will have a lot of available sugars (mono and di-saccharides), that will fuel a bacterial bloom, again using oxygen and giving them a high BOD.
Plant leaves are in the middle in terms of BOD, they contain sugars and starch (from photosynthesis), and the chlorophyll protein itself, but they also contain structural carbohydrates (cellulose etc) that are less easily degraded. If a plant is going to shed a leaf, it removes the proteins and carbohydrates first, which is why the leaf changes colour. If a leaf is damaged, proteins and sugars will leak out and bacterial decomposition will occur.
Wood has the least BOD, it is dead tissue and it has no sugars or proteins, and much of the structure has become lignified. Lignin is degradable, but only by certain organisms, mainly because the amount of energy that you put in is almost as great as the amount of energy that you get out. This means that its BOD is negligible.
cheers Darrel