_Pure_ water has a pH of 7.0. But that's an extremely difficult measurement, and almost irrelevant for fish-keeping ('cuz anthing else in the water will change it). Breathe on it, and you'll lower the pH... to about 5.5, which is the pH you'll get with atmospheric CO2 dissolved in it ;) michael kahlow -----Original Message----- From: owner-apisto@admin.listbox.com [mailto:owner-apisto@admin.listbox.com]On Behalf Of JerrCarol@aol.com Sent: Monday, March 25, 2002 12:15 PM To: apisto@listbox.com Subject: Re: Reconstituting RO/DI Water/ RO Water comes in at 5.5pH Pertaining to the pH of RO water. One of the guys at my fish club is a lab tech at Aquarium Pharm. While he does agree you can't use the test equipment at home whether it be electronic or liquid test to measure pH. Apparently they have something in the lab they can measure it with. He told me there is no such thing as pure RO and when measured with whatever equipment they use it comes in at 5.5pH. Just what I was told... Not what I know for fact but, this guy is a pretty up there fish guy. JerryB. ------------------------------------------------------------------------- This is the apistogramma mailing list, apisto@listbox.com. For instructions on how to subscribe or unsubscribe or get help, email apisto-request@listbox.com. apisto-digest@listbox.com also available. Web archives at http://lists.thekrib.com/apisto