Quote Originally Posted by ~pete~
and arent CA Reactors adding more?
I don't think so if they're working correctly; however, they can contribute to ph drops because of the low ph of the effluent. Ideally, I think the CO2 that's injected into a reactor and dissolved in the water turns into carbonic acid and reacts with the carbonate media, thus it's not entering the tank as dissolved CO2. I'm sure in reality, though, a little gets in there. It "should" get neutralized by the increased presence of carbonate in the effluent.

Ironically, CO2 provides the source for carbonate in calcification, and so it is necessary for coral growth. However, when the CO2 dissociates into carbonate, a bi-product is a hydrogen ion, which is responsible for the ph drop. Too much of this and the low ph inhibits calcification. So thunderkat is right in that the title is a little misleading; it should say "CO2 lowers ph which then inhibits coral growth" but then only us reef geeks would read the story.

As Gary said, atmospheric CO2 from a sealed crowded house is much more likely to cause ph problems than a well adjusted CA reactor.