Andy Pierce
Member
If you needed to pick one, I would go with CO2. There are plants you just can't grow without CO2 (e.g. carpeting) but there aren't really a lot of plants that won't grow because you can't get them enough (or sufficiently controlled) light. People are right to point out that proper flow should be considered a part of CO2 implementation to avoid causing more problems than the CO2 will solve. CO2 is in general "high maintenance" mentally so be ready to commit to that if that's the way you decide to go.
