Here are some close ups of the bottles and what they do.
As the diet coke bottle fills up, the weight causes it to pull on a fishing line (25 lb test) which, through a series of pulleys closes the valve (small black thing in the picture in the previous post.
It also aerates the water, I think pretty good. there are 6 holes drilled in the bottom of the diet coke bottle, that allow for drainage and aeration.
When the valve is closed, water is forced up the 2 45 degree elbows and flows into the left grow bed. When the auto-siphon kicks in, it fills up a Pepsi bottle and eventually opens the valve, allowing water back into the right side grow bed.
Don't have water in the FT yet, as I have some more gluing to do on the 3 1/2 PVC Trough.