Thanks for the answer. I just tested my PH and it's at 6.4 so it's not dropping all the much on the daily basis.
I don't think that it is the pH that you have to worry about dropping too far.
The pH drop with Akadama seems to be smaller than with ADA soils but the pH does seem to hold stable with Akadama.
The gH and kH are what you have to worry about.
I am guessing (but haven't tested it yet) that with tap water it probably isn't as much of an issue for two reasons - tap water tanks probably don't have as sensitive of shrimp (or they would be RO tanks) and the vast majority of tap water is going to come with higher TDS/gH/kH than what people set their RO water to.
If you look at what people are reconstituting RO water at (TDS/gH/kH levels) for most of the caridina cantonensis (bee shrimp and tigers) and caridina serrata shrimp (TTs, Aura Blues) there is very little TDS/gH/kH to spare so percentage wise any change is pretty significant.
People are re-constituting their RO water to mineral levels that are pretty close to zero to start with so there just isn't much leeway.