Well, after several calls to the supplier I got the Gast pump replaced and finally installed the diffuser last Wednesday. It's now running 24/7 at a depth of 20 + feet with a good boil. I have plenty of weighted hose left and may install an array of 9" diffusers at the opposite end of the pond.
I have noticed a slight difference in the clarity of the water, although it might be just wishful thinking.
I was wondering what the turnover rate would be for the current system and what the rate would be if I were to install the array of 9" round diffusers.
I'll try and post some pics.