Hallo Vale!
Thank you very much for your long post!!!
Here I try to answer step by step:
1. I use as the title of the threat says, dry black peat granule (pressed material) in a little filter bag.
2. This morning I ve measured nitrite with photometer, and the paro tank has 0,6, the selatanensis tank 1, 4.
3. I´ve taken out today old alder cones, a half resolved catappa leaf, and moss. I see, I should do that more often …
4. If the turbidity really is just caused by fulvic acid from the plant materials, I think it will be o.k. for the fish – I just read that the black water would be coloured but very clear …
5. I´ve found a dip slide test for water beds 😉 and it measures aerobe bacterias, I have ordered it …