Iris Cohen,
mentioned the Ball Bearing effect, on IBC. The idea being that all the inorganic particles have roughly the same size and being smooth, like ball bearings. Another lady in Europe, uses the Lecca balls.
So we tested the idea. Using aquarium "gravel" from China, and a small quantity of compost, on a local willow leaf type ficus. The expected situation is that the compost will slowly "melt" and the roots will take over the exmpty space.
The result for the first year has been positive, though the roots keep expanding and throwing out the stones.
With this ficus, no problems were encountered with the plant falling out of the container, in strong breezes.
The pot is also one of those Chinese types with a coarse interior.
If it were smooth on the interior, then a tool would have been used to leave furrows on the inside.
As a plus, the roots also locked down the moss.
Anyhow, thus far, it works. Growth on the tree is constant and drainage excellent.
Additionally, a local stone type that is like a hardened porous clay, bonded with calcium, also at the same size of particles, will grow a Tamarind. The organic part is sprinkled on by the spoonfuls, and left to decay in.
I have hired a large centipede [ as we call them, a congaree ] to deliver rounded particles of fecal matter. So I am using that as the organic material.
Will keep the group informed.
Good Evening.
Anthony