That sounds very cool. So you just have the coco in there for a preliminary substrate. That makes sense. I was using rapid rooters as mine.
I found the airstone became unnecessary with constant flow.

If you want to see some waterfall NFT action, check this thread:
http://boards.cannabis.com/grow-log/...-darkside.html

That was my own learning experience and I am setting it up again for another run as soon as the hydroton is clean. It's sitting in some Cannazyme as we speak! w00t~