I have an idea for the way I would like to build my system, would like any feedback as I am sure someone has tried this. But here is my plan so far, drawing out a design I will post if anyone wants to see it.

1) The idea is to have a high central fish tank to let gravity pull water into the grow beds for the plants with a tumbler/inclosed fan blade to break up solids as it goes down.
2) From the grow beds it would go down into a sump tank which at the bottom would have a diy Hydraulic ram pump to pump the water by its own gravity force back into the top of the fish tank.
with a float to cut off water to the pump if the water gets to high.

I wonder about the air pump I was reading in the 101 posts (Awesome threads btw Oliver)
Do you guys think that there could be enough pressure from the gravity feeding to power a air pump for the tank? Or is there any non-gird powered way to feed air into the water, again the idea is to be self contained incase the power ever stops.
and I hope this is the right place to post this.

Thanks