Ingrid,

I am interested that you prefer 10-12" for the veggie filter. What
guides your choice of depth?

We went with two 8" boards for depth. They seem to be working fine.
Our water celery and hyacinth send roots down essentially all 18" of
our veggie filter depth. I think that increases the filtering and the
catching of muck. They would fill faster at 10-12".

Jim