Hi, Steffen, as Peter tells, some chemicals are dangerous and we have already too much of them in our world.
Our water here near Freiburg has about EC 220, so an osmosis plant works fine. But even with an EC of about 60 I get a pH value of 4,5-5,3. (Yes, it depends on the dKh value …)
Look for Pawels water recipe here: “As I started to think much more about ecology when I became a member here and did not want to use peat in large amounts anymore, I prepare my water like this: (reciepe for 10 liters) 1 liter alder cone extract (let infuse big handful of alder cones in 1 liter RO water for a week) 1 liter Ketapang extract (Terminalia catapa leaves extract prepared the same way as previous, if you want to use it make sure to order the real stuff from Asia, brown red and honey smell, sometimes they sell almost green leaves collected right from the trees and that is just useless) and 1 ml of Aquahum (artificialy prepared solution of 50:50 humic and fulvic acids made by humidifying celulose leftovers after paper production under laboratory conditions) ad RO water to the amount of 10 liters. Of course you do not have to make such semilabarotary tricks and you may use just peat and add beech leaves in to the tank. It works fine, just be aware that soft and acidic is not enough, you need to use humic substances too.”
As I don’t need so much stuff for my few tanks, I take a two liter glass bowl, put into it a piece of cattappa leaves, a small handful of elder cones, two oak leaves. I let it rest for one day, and then I add it to the water change – water. That’s enough. With Aquahum I am now very careful, if I use it, I take maximum one drop for 5l water, because I suspect that it colors the filaments of the fish with black spots.
I don’t use peat anymore.