That has long been debated wether a sandbed which is for the most part "idle", has any effect on the buffering capability of the system.
IMO, a sandbed is more useful as a media for bacterial filtration. Most
aragonites don't break down until the
pH has been dropped down to around 6.5 or so, which is why we use Co2 in our
Ca Reactors. Since the
pH in our tanks is hopefully higher than that, I wouldn't expect any buffering to be done by your
aragonite sand bed.
