DIY... When leaves, branches, or other things fall into the water they begin the process of decomposition. One of the byproducts of decomposition is co2. So it would stand to reason that if you had a tank with lots of decomposing matter such as leaf litter and a dirt substrate,
Has anyone done this before, or know of a thread that already discussed this?
If you think about it, the process of yeast fermentation used in DIY is pretty close to your decomposition idea... transform complex sugars to CO2, but faster and cleaner for your tank.
The problem with decomposition is that it needs large amounts of O2 to prevent it from going anaerobic.... to add O2 to aquariums you will increase surface movement therefore reducing CO2 conc--- bottom line 0 gain. True, CO2 is a byproduct but so will be H2S and CH4... things that might make your aquarium not that fun to keep in the living room. Also you will have a good amount of debris all over the aquarium, including on plants.
From what I can remember from Walstad's book, she recommends that the substrate not be very rich in unprocessed organic matter precisely for the reasons above.
Bottom line, my position is that we should understand what happens in nature, but stop trying to reproduce it in our aquariums. Our aquariums lack the space and complexity of natural beautiful ecosystem. Furthermore, most of us do not want the huge monoculture patches, fine debris on leaves, seasonal changes, predation etc.
If you want to try it out, all the best and post it. Data on experiments is always nice to have, even if they fail.