C02, effect on ph?

I have read a bit on this but , I am not quite getting it. Any who has a good understanding of C02's affect on ph, please shed some light on this for me.

Well I can't explain how but.... I know that harder water has a lower level of disolved carbon dioxide and softer water has a higher level. So adding disolved co2 to a system will lower the ph. I don't know how the process or how it does it. All I know is it does. I have seen it in both my planted tanks when I added co2. There was a drop in ph of .4 in one tank and .6 in the other. Sorry that wasent much help. Are you having some sort of issue with the ph in a tank you are adding co2 to?

haven't done c02 yet ,, hell haven't planted yet. just getting educated.

Ahhh so your doing it the right way. Awsome.

I recently had a very similar question about my well water pH. I was puzzled because my well water was coming out of the tap at 6.6, and after a week of sitting in a rain barrel it tested around 7.5. This is the answer I got from one of the experts over at TFK.com.

"It would seem that you have a considerable amount of dissolved carbon dioxide (CO2) in your well water. This often occurs in tap water too, which is why it is recommended to let tap water sit for 24 hours before testing the pH, as this gives the CO2 the time to dissipate from the water. CO2 lowers pH because it is adding acid, and when it dissipates from the water the pH rises. This is the same in reverse as when planted tank aquarists add diffused CO2 to their tanks, it lowers the pH."

"Sometimes objects in the tank that are calcareous (rock or gravel made from calcareous rock, coral, dolomite, marble, lava, etc) are the culprits but in this case you have tested the water on its own, so I suspect the CO2 is the answer."

Co2 makes an intermediate called carboxyl acid in high "dissolved" levels. It then litterally acts as an acid in your tank by displacing -oh (hydroxides) with h+ (hydrogen ions).

...that is why ph in co2 sytems often drops qiute a lot at night. Plants aren't photosynthesizing and using "free" carbon to build sugars and cellulose(really chiral sugars if u think about it). The unused co2 makes acids. Most people turn off with timer/celliniod co2 at night or at least reduce bubble count to prevent night ph crash.