Interesting to learn about the flourine. I've only just started to use perlite after learning that it is mildly alkaline and being in need of more alkaline conditions for some species I was planting from seed. I think I even added it to the mix for some asiatic seed as I figured they weren't too fussed about pH. and I had run out vermiculite.
It hasn't been long enough to tell if they are suffering....
