Warning! Potential Problem with Kent Salt.

[Beverly]

Ruth,

The RO/DI water had been heated and aerated since last Sunday after the water change. The salt was added, fully dissolved, then aerated for about 20-30 minutes before testing.

BTW, we mix the salt into the heated and fully aerated RO/DI water not longer than 24 hours before using. After about 36 hours, we've noticed that something precipitates out of the salted water, which could explain your different readings. Or, if you start out with cool, unaerated RO water when you add the salt, you could also get different readings after it has been aerated and heated with the salt in it.