Rocks and My Chids
 

Rocks are becoming my favorite medium. It drains well and at the same time holds more water than you might think. I have three choices, Granite chips/pieces, lava rock and pea gravel. I use more granite bec it come in all sizes in 1 bag :D ,only cost 3 dollars for about 50 lbs of it.
So you think Granite cant hold water just bec its a rock? :rofl:....You are in for a BIG soooprise :bowing

I once tried using glass beads to help drainage at the bottom of the pot. They did the opposite!

What I worked out is that water clung in the gaps between them and because it was not absorbed by the glass stayed as larger drops and dried out slower.

I think rock has the same thing to a greater extent because as well as gaps between the pieces there is all the crevices in the pieces themselves. Those have water clinging in them which because it can't go anywhere dries out slower.

That's what I've seen from observation, however it still does seem counter intuitive that rock medium can work well and hold water for chids.

Just be careful that the pieces are big enough that they provide large air spaces between them, or the "bridging water" Rosie described will suffocate the roots as well as a decomposed bark medium.