reactor media and ph

[fishpoo]

Hi Randy,
i started up my reactor after laying dormant for sometime (me and the reactor, LOL)
i'm using a brand called ARM and directions state to set reactor ph to 7.5. How can CO2 melt aragonite at such a high ph? If it does work, wouldn't it take considerably longer? thanks tom.

[Randy Holmes-Farley]

Tom:

I presume that you are setting the pH after the aragonite partially dissolves. Dissolving the CaCO3 releases CO3-- which raises the pH.

So it might have been 7.0 hitting the aragonite, but as some CO3-- is released, it maxs out at about 7.5.

FWIW, aragonite is soluble at pH 7.5. About 7.5 to 7.7 is the solubility limit in our tanks. I show this in an upcoming article on calcium.