there is an old saying, that "adding CO2, is beneficial, ONLY if everything else is 'just right' " ... dunno if that's true, but I add 'hillbilly' CO2, and can't honestly say that I've seen a bit of difference ... but, I just do the sugar/yeast thing, costs only pennies, and does SEEM to add CO2 in the cabinet, no way of measuring the output ... :smokin: