Flourish Excel? is a source of bioavailable organic carbon. All plants require a source of carbon. This is typically obtained from CO2, but, may also be derived from simple organic compounds (such as photosynthetic intermediates). Therefore, 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 an integral component of Seachem?s plant products and is recommended for use with the entire Flourish? line as well as our Flourite? and Onyx Sand? substrates. Contains no phosphate or nitrate.