wouldnt rock also store phosphates and metals then, if it was performing denitrification? i have plenty of rock, both in tank and first chamber of sump. i wonder if this will be enough..... anyone else have an opinion on the aragonite - PH thing, or see any pitfalls with removing sand / plants in fuge, leaving tank completely sandless?
if sand was used in a fluidised form, then surely it wouldnt store phosphates etc nearly as much as if crud was allowed to settle on it, as with a sand bed, only react to the ph changes and [depending on whose side you take] release carbonate.....