Typically RO/DI product water is around 7.0. But with very pure water there can be a lot of inaccuracies with readings.
Pure water also doesn't have a very "developed" buffering capacity so it can be very variable depending on outside influences.
A high
pH of
RO/DI water mixed with a solid 8.2
SW mix will not bring the new
pH to an average between the two. The buffering capacity of the
SW will lower the
pH of the
RO/DI significantly.
There is also a reaction/conversion of
ammonia and cloramines of the tap water pretreatment that can result in a higher
pH... I forget the exact mechanism at the moment.
What is the
pH of your display tank? That would be the most valuable piece of information. If it is normal than let everything be. If you start messing with chemistry based on the possible inaccruate
pH reading you will throw everything out of whack and it is hard to recover from that.
There is talk of the resulting
pH from a
SW mix will be increased in the future to a minimum of 8.4. We keep the
pH of our tanks on the hairy edge of low for the most part.
It's not something I would worry about or alter unless there is problems with your reading in your display.
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