Seachem 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. 250 mL will treat a 50 gallon tank for 1-2 months