Planted Tank Guru
Join Date: Dec 2002
Location: Portland Orygun
Fish will contribute a small amount of CO2. Plants can grow without CO2. But some plants that are more light demanding also require the use of CO2. CO2 in a planted aquarium is a lot of like N2O in an engine. It drives the plants faster and helps control algae.
If you can raise the CO2 levels 3-4 ppm it will help. As much as getting them into a higher range? I doubt it.