Flourish Excel provides readily available organic carbon to your plants. The typical source of carbon is CO2 which may come from fish, decomposing organic matter, air or even though injection of CO2. All plants require a source of carbon and, our experience tells us, plants that receive supplemental CO2 grow more robust, are healthier and fight algea much better than the plants that do not. You can use Flourish Excel either alone or together with with CO2 injection. Flourish Excel also has iron reducing properties which promote the ferrous state of iron (fe+2), which is more easily utilized by plants than ferric iron (fe+3).