CO2 for ph down?!?

I was reading that in big aquariums they use CO2 to ph down the water. I was a bit confused by this. Then it got me thinking, i already have a CO2 tank. Has anyone tried this? if so what were the results? Does know of any bad results by adding CO2 to the water?? i haven't tried this yet, i just purchased a ph controller and was curious about it.

Carbon dioxide in water forms carbonic acid which is a weak acid. There are better alternatives and CO2 isn't really good for the roots; they breathe oxygen.

Nullis said:

Carbon dioxide in water forms carbonic acid which is a weak acid. There are better alternatives and CO2 isn't really good for the roots; they breathe oxygen.

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Thank you for the information. I have never ran hydro before, i will use a ph down solution.