Yes, interesting. Not stupid. I believe you are getting more net CO2 and, perhaps more importantly, more O2 into your water. Get the bubbles small enough (microbubbles) and everything will enter the water. It may not be a lot of CO2, maybe even a completely negligible amount, but it seems to me like it should be some amount higher than you would get atmospherically from a turbulence source. Maybe you are right, but higher O2 is my guess as to any true connection to less algae there may be. Having a non CO2 tank, I used to give this stuff a lot of thought. I settled on having all of my tank water leave the tank and go to the sump through surface skimming. This way the surface exchange membrane a) is always spottless and therefore as permeable as possible, and b) is moved back into circulation and quickly replaced with fresh, CO2 hungry water from below. Perhaps it is moot for me now as I am using Excel, but perhaps not. Any advance in higher CO2 levels for non injected tanks is a good thing. Interesting in any case.