Salut, tu es du Québec?
I use glutaraldehyde double dose, because it cost 50$ to refill a 10lbs cylinder in Quebec city. I would have to go to Laval to have a cheap CO2.
Results with glutaraldehyde are fair but cannot be compared to CO2, some plants seem to like it more than others. I have a 65G planted tank.
Hygrophila polypserma is thriving, so do the cryptocorynes but they were slow to adapt at first. Bacopa is good but not brillant, however it could be light related. Ludwigia is growing but not red, not in it's full magnificence.
Michel, but it's better than no C at all.