ph drop

[Aquattro]

Originally Posted by Rikko

Without your rock to buffer it, your pH would plummet to 5ish on its own.. It should plummet in time to the pH that the rock buffers to anyways.

Excuse me??? It most certainly would not plummet to 5ish, and rock does not, to any appreciable amount, buffer salt water.
You may see a drop to high 7s, with a large acid content (from ammonia byproducts) at which point aragonite may start to dissolve( I think the actual value is around pH 7.6 where aragonite starts to dissolve) and this in turn may act as a buffering agent to prevent it from going lower. Most tanks that experience regular partial water changes would not get to this point though.
As proof, my 25g tub that has my new water is at pH 8.1. After more than amonth of sitting in the tub, the water is still 8.1, no rock , no nothin'. It does not plummet to pH 5.