Do I need CO2 to grow plants in my aquarium?
In short no, but not all plants are equally undemanding. Slow-growing, green plants such as Java fern (Microsorium) and Anubias can thrive in very simple set-ups but fast-growing or delicate species can be a pale version of their more robust CO2 nurtured selves.
Broadly speaking, the use of CO2 enables a wider selection of plants to be grown and makes less demanding types even harder to kill. Typically, the highly coveted aquascaped layouts seen in books, magazines and the internet tend to feature CO2 systems.
An additional, often overlooked benefit of CO2 is that it gives rise to slightly acidic conditions that suit most species of fish that are likely to find themselves in a planted aquarium