Seachem Flourish Excel FAQ:
http://www.seachem.com/support/FAQs/FlourishExcel.html
"Q: Is Flourish Excel a replacement for CO2 in a planted aquarium?
A: Yes and no. It provides the same benefit as CO2, i.e. it provides the plants with a source of carbon for growth just as CO2 provides them with carbon. However CO2 by itself will give you quantitatively more growth than Excel by itself, although Excel does provide a substantial amount in comparison. If CO2 is a 10, Excel is a 6-7. Using both together provides additional benefit. One of the advantages of the Excel is no up front equipment costs and complexity of valves, hoses and regulators, etc."
Si am mai gasit asta:
http://www.simplyhydro.com/carbon_liquid.htm