I was reading earlier after supper about using vermiculite in potting mix that it helps keep the mix aerated. They also was saying that the container mix will settle over time. I was thinking just now that I did not put any vermiculite in the potting mix. May put some vermiculite in the top layer later when I add compost in the top layer above the charcoal layer, about a five inch layer.
A flash of thought occurred to me about how to aerate the lower part. I have an electric air pump just for tires I purchased in the spring. It has no tank and it is about the size of an electric drill. I could take a small tube about two feet long, crimp down one end to close off the end of the tube, make holes in the bottom 12 inches of the tube and on the upper end I could attach the attachment that came with the pump to fill basketballs. Hook the air pump to it, turn on the air pump and pump air down into the lower 12 inches of the mix which may fluff up the potting mix and create little air pockets. I have holes on the sides of the container and I could enter that way also. Save time of emptying the whole container and fluffing it up by hand.
Get some time I may set up the system for an experimental run.