If you are going to buy those tablets just mix
some baking soda and vinegar waaalaaaa Co2
but it is hard to control the amount you are
releasing. I seen a vinegar baking soda set
up in a small grow box that had a fish tank
regulator valve that controled the amount of
vinegar going into a bottle containing baking
soda. I still think it would be tricky to control
your ppm level that way also.