This is in no way my theory. Honestly, I have no desire to enter a debate with experts such as yourselves. I would lose every time! I just happen to be one of those people that aren't satisfied with doing A, B, and C to achieve Z. My curiosity gets the better of me most of the time. But if you read the articles posted and follow up on the references cited it's quite compelling. I never said allelopathy is the only factor involved between plant/algae ratios. I do however feel it is a factor. I only learned this because I don't buy into the competition only idea. In a planted aquarium there is no lack of nutrients or light. So quite simply there has to be other factors at play. I welcome explanations to the contrary or things I don't understand.
As far as I know activated charcoal does not effectively remove all organic compounds. In particular the more soluble ones such as alcohols and organic acids. In addition the compounds would have to exist only in the water column being filtered. This would exclude adhered compunds that may be present on plant structures as well as hardscape and substrate. I think to say all allelopathic compounds would be removed adequately by AC alone is erroneous. Then again I'm no expert lol.
According to articles and studies I have read there are numerous plants we cultivate that may have allelopathic properties; Potamogeton species, Eleocharis acicularis, Sagittaria subulata, Ceratophyllum demersum, Ceratophyllum muricatum, Hydrilla verticillata, Cabomba carolinia, Juncus repens, Limnobium spomgia, Brasenia schreberi, Vallisneria americana, Sparganium americanum.
This is a subject that has yet to be seriously studied in regards to the artificial world of the planted aquarium. It also happens to be a heavily debated arena. There is little monetray value in the expenditure of time and resources it would take to research it properly. That's the reason I have tried to extrapolate the information available related to this. It seems to me that sufficient evidence exists to support such a theory. Am I interpreting my readings inaccurately?
It is hard to prove a negative, so I doubt that anyone would say that there are no allelopathic compounds being produced by our plants. It should be possible to test that by doing the AC in the filter test, and if it does cause an algae bloom that would be compelling evidence that allelopathy exists in our tanks. And, any of us could do it if we wanted to do so. But, if it doesn't cause an algae bloom it doesn't definitely prove anything other than that any such compounds are either small molecules or aren't in solution in the water.
As I understand how activated carbon works, it adsorbs large molecules, and the method for preparing the carbon can be adjusted to make it adsorb a certain range of molecules. I doubt that the AC we buy in a LFS is prepared with that in mind, and it probably just adsorbs molecules bigger than "X", to a degree at least. I'm not a chemist, so I can't debate the subject very effectively in any case.
Incidentally, allelopathy in a planted tank is not a theory, but just a hypothesis, which can be tested. Now that is real nit picking