as i understand it coral or crushed coral rock will increase the ph ....im not sure that coal will alter the ph

the baking soda or bicarbonated soda will increase your kH and this is what buffers your waters ability to hold its ph.

are you sure your not getting things mixed up with marine calcium reactors im sure they use Co2 to disolve crushed coral ?

tjc have a look at this ph thread
Low ph

its related to what your asking i think
hth Robert

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