My way of thinking is that's the amount of CO2 a plant requires that determines if it will be successful, not overdoing the CO2 per se. Adding a cup of salt to popcorn won't make it taste better. Anyways, the internet says there are several sources of CO2 already in the aquarium. (the natural route) About one fifth of it is assimilated by the plants and returned to the water. The fish also add to the CO2 levels with their respiration. The bacterial decay of both dead plant material and driftwood decorations in the tank produce CO2. The largest contributor to CO2 levels in the aquarium is the biofilter which supposedly produces 1 gram of CO2 within a 24 hour cycle for every gram of dry food added to the tank.
Bump: Mixing plants from different habits with different requirements requires the stealth of a jedi. In a perfect world plants and fish that hang out together in nature will be the easiest to maintain.
