Hello,
the only plants I keep in my tanks are Java-fern, Anubias barteri var. nana, Java-moss and as floating plants Ceratopteris or Salvinia. They all seem to be able to cope with the water conditions. I use ro-water, that is dripping over peat, before I use it. The pH-value is around 5.
Besides there is a Cryptocoryne (I think it is C. pontederifolia), that i brought home from an IGL-convention, that is doing fine in a clay-pot filled with pure sand. It is growing very slow, but the leaves are healthy and green.
I don’t know exactly, what makes it work, perhaps it’s the moderate peatiness, compared to tanks with peat-substrate. Nevertheless it seems to be close to the limit.
Greetings
Martin