[Pavel Chaloupka]

Hello Dorothee,
I did not bother trying yet, but I think you should be able to get lower pH values than you do now. Sadly as long as we use any kind stuff such as alder cones or Terminalia catappa leaves, the results will never be fully comparable. The concetration of active substances may differ a lot and the acid neutralisation capacity of your water may differ from mine even thought we will end up with the same conductivity. Also keep in mind that the pH readings are not exact. I am not sure how much this fact is known, but if you want to measure pH in conductivity lower then 30µS you either should be using a special electrode (mostly possible only with laboratory devices that allow you to exchange electrodes. + the machine and the electrode is like 10x more expensive) to get exact readings OR (much easier 😉 ) you need to take some water from the tank and make the conductivity higher by adding small amount of KCl (3M KCl electrode storing solution) or NaCl. Than you get acurate readings even with the types of devices we use for our purposes (within the boundaries of the device). So we have to be careful about how acurate we can expect our readings to be.
Anyways if you need extreme pH, I am sure we would be able to come up with some good kation exchanger resin to prepare such water, that would be easy to use and one could use it for years. The principle is the same as with peat, which is (or more precisely humic acids in it) kation exchanger too besides leaching out some acids in the first place. On the other hand, the Ketapang leaves extract has such a strong antibacterial effect that lower pH values very likely would not be needed.