It's not the number of plants so much as the intensity of the light. If you are doing low light I believe you could just make sure you have adequate water movement to ensure CO2 doesn't fall below ambient levels.
You can also do away with the bubble wand. That will gas out any co2 that is in the tank. That said, you don't really need the co2, though you might need a little more light.
You can also do away with the bubble wand. That will gas out any co2 that is in the tank. That said, you don't really need the co2, though you might need a little more light.
Aeration will outgas CO2 when levels are above ambient atmospheric levels in the tank. If CO2 levels are below ambient levels then aeration will actually increase CO2 content in the water. I've never been sold on the idea that fish and bacterial respiration add any real benefit to a planted tank.