Hello Jacob,
1. I also use R/O water. Our tap water is very hard (>45°GH), so the permeate still has a cunductance of about 70,0 microsiemens/cm. What works best for me is to use something like this:
The R/O water drips over peat (unfertilized, pure) filled in a bottle, right when it exits the R/O unit. After this I get yellowih water with pH around 4.5 and a cunductance around 50 microsiemens/cm. The initial murkiness vanishes in the tank, a few hours after the water change.
I made the experience, that anything that has to do with adding something to R/O water, like peat-extract etc. makes you end up with too high conductances…
so I prefer the dripping method, which extracts the humic acids from the peat and on the other hand even lowers the conductance.
Perhaps there are other ways of getting a suitable water, especially if you have softer tap water, but in my case, this method seems best.
2. I’ve never watched a pH-crash in my tanks up to now… I think, the humic acids and other sunbstances of peat, leaves etc. buffer the pH at a certain level.
What I experienced is the exact opposite: in newly setup tanks, it can be the case that pH-levels rise again, after water-change. Perhaps that’s because the biological system in the tank has to find its balance?
Of course you don’t need to filter or cycle your setup if you add plants with submerged roots, but I prefer a little circulation, so I use small sponge-filters. But thats due to my subjective feeling.
3. In my opinion, moina and artemia (freshly hatched) makes a good staple. You can add all sorts of mosquito larvae if they are not too big for the paros…
I don’t know blackworm yet, but if they are not too big, it should work… try it.
Good luck with your setup.
Martin