Seachem Flourish Excel
The most popular alternative to CO2 injection for high growth tanks.
Uses: Flourish Excel™ acts as an alternative to CO2 injection in "low tech" tanks. Used at standard dosage, it can often double the growth rate of plants and provide for much denser and healthier plant growth. If you keep any plants that are somewhat demanding or are just interested in increased the growth rate of your planted tank, Flourish Excel™ is an excellent choice. We use this at Aquatic Arts in all of our commercial aquatic plant systems as pressurized CO2 is not practical for us (as it is not practical for most people). Consider using with our other Seachem products!
From the manufacturer: 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). The use of either CO2 injection or Flourish Excel™ does not necessarily negate the use of the other. Because the processes of producing photosynthetic intermediates and building onto them occur simultaneously, one can derive a substantial benefit with the use of Flourish Excel™ either alone or in conjunction with CO2 . The combination is particularly ideal for situations when continuing to add CO2 could result in dangerously low pH levels. 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).
Directions from the manufacturer: 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.