I appreciate your continued help.

The Kem Tek is no longer available from Amazon. I see from the MSDS that the Kem Tek one is 7% lanthanum chloride. The Orenda PR-10000 lists 'proprietary" chemical composition. PHOSfree by Natural Chemistry lists 7-13% lanthanum chloride. Have you heard anything about that one?

It occurred to me that the town switched to a communal well earlier last year. Previously, we were receiving water from a nearby industrial mill. Not that I am assigning blame, but that would explain why we never had an algae problem until last summer.