Sorry for the double post - working and forgot to respond with the rest - it's nice to see someone else using a pH controller here. It seems that they're uncommon on UKAPS. I also run remin. RO and KH is almost nil. I ended up recalibrating my pH controller to read higher than the actual pH to avoid using an alkaline buffer. IE, calibrating the probe so that the 7.01 standard is interpreted as 7.3. , 4.01 as 4.3. Let's me push it a bit lower than the controller actually goes as the controller function on mine only goes down to 5.5. In hindsight, probably should've just added some KH lol. Maybe I'll start now.