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. DIRECTIONS: On initial use or after a major (> 40%) water change, use 1 capful (5 mL) for every 40 L (10 gallons*). Thereafter use 1 capful for every 200 L (50 gallons*) daily or every other day. Dosing may be slowly increased in high-growth aquariums. For smaller dosing please note that each cap thread is approximately 1 mL.