I saw your message about the how the pH of your tap water changed when you moved [from Capitol Hill to Greenwood]. I work for the Seattle Public Utilities (formerly the Seattle Water Department) in the Cedar River Watershed near North Bend. In general, City residents who live north of the Ship Canal get their water from the South Fork of the Tolt River. Those who live south of the Ship Canal (like I do, right near the Locks) get their water from the Cedar River. That probably explains the difference that you experienced when you moved.
By filtering over Peat (I put it in the extra media holders that came with my Marineland Emperor 400 power filter), I too can bring my pH down to the low 6’s, but have to add acid to get it lower. I have been using a product made by Fritz called pH Down, to get the pH a little lower. When David Soares spoke at the GSAS Meeting last November, he told me that he used Sodium Biphospate to get his pH’s way down under certain circumstances.
- Keith Kurko
[Editor’s note: we have used Seachem’s Acid Buffer, probably containing sulphuric acid, to drop pH below 6.0.]