Olga, Air pollution could produce rapid large changes in the pH of unbuffered water, but without knowing what pollutants your water is exposed to it is impossible to calculate what pH changes could result. It is also hard to reconcile an air-pollution cause with the light/dark cycle you mentioned; I assume the same water is in contact with the same air, regardless of wether it is stored in the light or dark ?
I'm out of ideas. If your water is unbuffered, slightly acidic to start with & has no plants, then a 10 degree temp rise should produce a pH drop of less than half a unit. How accurate is your pH meter ? Do you calibrate it every time you turn it on and use it ? Peter O'Byrne Singapore _______________________________________________ the OrchidGuide Digest (OGD) [EMAIL PROTECTED] http://lists.orchidguide.com/mailman/listinfo/orchids
