the co2 works by adding sugar water and yeast, as the yeast feed off the sugar it produces co2 which is then entered into the tank throught the air hose on a small powerhead. I went low tech but i dont really know how much co2 it's putting out. the indicator ihave is still light green more on the yellowish side i might just upgrade to a presurised system . but i'm gonna give this one a go for a few months and see what happens, i mean i can always just add another lo tech one or make my own.