Dear Baja_Costero,
Thanks again for your very detailed post!
I think my biggest challenge is that I don't know exactly how much grit I need to add--is 50% soil and 50% grit a good proportion? Our soil seems pretty muddy. It comes in part from a super good soil that was brought to us by some landscapers who helped us build a structure for a passion fruit tree a year ago. So obviously, they didn't think we needed well draining soil :)
From your post I have learned that I need a thicker layer of "good soil" (and not just a bit added on top), although I see that the aeoniums that I've had for a year have very short roots (despite their disproportionately tall stems). Is that not the case with the other "creatures" you see on my picture? How about a 10''-layer of good soil? I could mix the grit in those 10'' (below that would be the thin non-modified soil).
Regarding grit, it seems I can use perlite or pumice but the latter is better for the environment although more expensive, correct?
