Flourish Excel - 250 ml Flourish Excel is a simple source of readily available organic carbon. All plants require a source of carbon. This is typically obtained from CO2 but may also be obtained via relatively simple organic compounds (such as photosynthetic intermediates). Since both processes occur simultaneously one can derive a substantial benefit with the use of Flourish Excel either alone or in conjunction 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). Flourish Excel is recommended for use with the entire family of Flourish products as well as our gravel, Fluorite , our Gh builder, Equilibrium , and our non-phosphate buffers, acid buffer & alkaline buffer . 250 ml will treat 50 gallons for 1-2 months.