okay closed loop circuit thing as described by melev is done.
I tried out the swirls and even though they didn't directly point to the floor they stirred up quite a bit of my super fine sand. Went and got some coarser sand (just to put a thin layer over the fine sand to keep it down) at AD and also a dual loc-line output to split up the output stream from one strong one into two weaker ones. That seemed to solve the sand blasting problem but I still get micro bubbles.
The only source of air in this closed loop design could be that primer pipe. Obviously I can't completely fill this with air (since it drains through the input pipe back into the tank)
Can I assume eventually all this air is used up and then it stops doing this?
How long is this going to continue?