I just found out this incredible thing today. Using CO2 to control ph. Mountainman talked about getting a controller to build a ph adjusting machine. Someone posting about using CO2 to control ph. Armed with my new soda club machine ($79 Edition 1) I was ready for the challenge. Today I measured tap water with CO2 and without CO2. The same with R/O water. Seltzer water is plain water injected with CO2. Here are my results. Tap water with CO2 5.4, 5.0, 5.0 5.1 Tap water without CO2 7.1, 7.1 7.9 8.0 R/O water with CO2 4.4, 4.4, 4.5, 4.5 R/O water without CO2 8.0, 6.0, 8.2 8.3 I injected CO2 till the machine farted. Serious folks. The machine makes a farting noise when no more CO2 can be injected into the water, but without the smell. Amazing. I used this same bottle of water all day and did not change the tap water sample or R/O sample during this experiment. There is an errant number in R/O without CO2 which might be due to ph meter error. I did check it three different times. I used the same ph meter throughout this experiment. CO2 stabilizes ph and brings it down and holds it steady. The hydroponics industry already knows this and is using this technology. Hence we have ph meters using CO2 to control ph. Look at the range at both tap water and R/O water with CO2. Remarkable, the CO2 holds it steady and when compared to the same type of water without CO2 you see the increase in ph. Look at the figures for tap and R/O water without CO2. The ph is very alkaline and the nutrients are not available at this ph level. Inject CO2 into water and look at the results. Lowered ph levels to perfect range for mj plants. ph 5.0-6.0. And so far pretty constant. Now we know why the ph steadily rises. The plants is using up CO2. So yes the roots do take up CO2. The whole plant is a CO2 consuming factory. So getting to the bottom line. CO2 does make a big difference. Maybe people can stop using dangerous chemicals (muriatic acid) to control ph and just use CO2 to bring ph down. I never felt good about giving my plants all that vinegar to control ph. If you poured straight vinegar on a plants root, it would die.