Thanks, John! That's what I was planning. I'm thinking there shouldn't be much growing straight down since it's an air layer.
Now, soil...
Back in the day, I had never heard of akadama. I used turface.
I now have akadama (double red line brand) and some Beam Clay brand pumice.
I also have an unlimited supply of granite grit that I can seive out of my horse arena.
And, back in the day, we used to put in about 1/3 organics in the form of "Natures Helper". But, I'm thinking the modern thought is to forego the organics entirely?