Hm, I don't think I add more then necessary. Even in the pinned thread about which soils to use they talk about this stuff (dolomit, potash and crushed shells). I'll just add a bit of KCO3, crushed egg shells and Dolomit powder to my potting organic soil mixed with garden top soil and cap it with my gravel. Nothing really complicated and how I did all the other tanks. I just made a list of things I bought to get a feeling how expensive this project is. Maybe thats where the confusion stemms from?
I also didn't really need to tweak anything so far, the tanks run very smoothly (except the one with the cloudiness and that does only affect the looks).
Hello. I'm looking forward to seeing how your tank works out. Your water situation is very different from ours and most of the U.S.. Only on the west coast, in parts of California, Washington state and Oregon, do we see naturally soft water like yours. So even though this is a Walstad type forum here, not many of us deal with your water issues.
There is a fellow online who has a fish shop, (selling all things aquarium-related) in Washington state, his name is Corey something, and he has a YouTube channel you might find helpful. Perhaps you've already found him? His channel and store are both called Aquarium Co-op. I think to get to his online store you just type aquariumcoop dot com. He is very knowledgeable about most things aquarium-related, especially in dealing with water like yours. He likes Walstad style tanks a lot and uses them where he can. But I thought since he has very similar water to you, you might gain some insight as to what works and what doesn't when deviating from the simple 'dirt on the bottom, gravel on top, add water and fish and you're done' style of fish keeping. He rambles quite a lot but his rambling is filled with solid experience based on those hundreds of tanks he runs and has run for years. I've learned so many tips from the guy, I find him to be a goldmine of information.
I have Nymphoides sp. Taiwan as well. Mine recently started putting out lily-pad like leaves. They are more arrowhead shaped and less wavy than the submerged leaves. They also have very long stems that are developing plantlets at a point about an inch behind the leaf. Have you seen this in yours yet?