Co2 As A Way Of Controlling Ph?

[MnMargo]

I have discus fish. Everyone says I have to buy an RO system. However, I recently heard that instead I can use CO2 to control the PH in my discus tank. Has anyone done this? I want to have a planted acquarium so if I can use CO2 to control PH then I can achieve both aims with the CO2 and not have to deal with RO.

Currently I am buying RO water for my partial water changes; mixing it with tap. But I hear that is inherently unstable unless I buffer it. This is a little above my head so can someone explain how using CO2 might help regulate PH?

 

[Liam]

Welcome to the forum.
Yeah Co2 will lower PH but a point drop is as much as you can safely achieve, from 8 to 7 for example, it does this by making carbonic acid. With Discus the hardness or (total disolved solids TDS) of the water is as or more important than the ph, softer water has lower ph, in a way ph is as much a measure of water hardness as of ph for discus water. I don’t think that discus eggs would hatch for example in harder water that had its ph reduced by Co2, its about osmoregulation the balance of salts in the fish and the water. If your water is hard then mixing it with RO water will be enough to buffer it. All that the buffering products do is add back some of the buffering that have been removed by the ro filter. For really clean water, with no heavy metals or nitrates you could use something like Kent RO right to add back essential minerals and buffering (calcium carbonate)
New world Cichlids here is the page for discus questions, (you will get a better response rate there)