I've always wondered about the lengths that aquarists go to insert CO2 into their systems, and the inherent risks that both Pressurized CO2 tanks and Glutaraldehyde (Excel) carry with them.
What I find interesting is that we add all of this complexity to the system to emulate a natural system which is much more elegant. Aquatic plants in the wild do just fine without the luxury of CO2 enrichment. If I understand correctly it is because an planted tank represents a plant density which rivers and lakes will never approach, so the ratio of surface area to plant biomass is much much higher in nature which keeps sufficient CO2 in the system simply from gas exchange (which is limited by surface area).
With that assumption, has anyone ever tried to artificially increase the surface area of their tank until the passive gas exchange was enough to maintain healthy CO2 levels?
I'm no chemist, so I don't know how much you would have to increase surface area to start seeing a measurable effect. However I would think it would be relatively simple to double or triple the surface area in your system without taking up much more space. If you had a 40 gallon breeder, and you plumbed (carefully) an overflow to take the water from the main tank into a 10 gallon tank with shallow trays spaced every half inch you would increase the surface area of your system by a factor of 7 or so. Seeing as how a 40 gallon breeder is 36x18=648 square inches of surface area, and a 10 gallon has a 20x10=200 square inch surface area with a depth of 12 inches which would accommodate 24 half inch trays for a total of 4800 additional square inches of surface area.
Its really no different from plumbing up a very strange sump, its eminently doable and no stranger than the sort of stuff they dream up on the Saltwater side of the hobby. Heck it may be overkill to even glue acrylic trays into a tank, you might be able to get away with placing a large extremely fine sponge in the supplementary tank and just running water slowly through that.
Does this concept seem like it may be valid? The only thing I can think of is that I might be vastly underestimating the additional surface area required to get this to work, but it really seems doable to VASTLY increase the surface area of the tank with very little additional space devoted to the setup.