My KH director was always reading 6.9 - 7.1 when my Hanna, Salifert, and Red Sea kits were all reading 9.0. I figured this is just testing difference. I keep my Alk very stable and used the Director for monitoring only. I recently decided to bring my Alk down to 8.0 due to low nutrients and burning the tips on some acros. Over the course the of a few days I lowered the amount of dosing and as expected my test kits showed my alk dropping. It dropped down to 7.6 and I added carbonate to get back to 8.0 and have been holding steady there. All my manual test kits (hanna, Salifert, Red Sea) showed the drop in Alk to 7.6 and the subsequent increase back to 8.0 as expected. The KH Director on the other hand stayed reading between 6.9 - 7.1 this whole time. During this time I calibrated the pH probe, re-measured my tubes, made sure no air bubbles anywhere, calibrated the Doser, but it made no difference. Always reading 6.9 - 7.1. I put a ticket in (#814) but haven't heard back about it. Anyone else experience anything like this?
