I'm so far from an expert it isn't funny, but isn't just the fact that the aerators are doing their job by circulating the entire BOW that it's picking up the top layer of sediment? Which as Theodore eluded to is promoting the muck to decompose? Which seems to be an added benefit of aeration.
I'm thinking that even if the diffusers are raised off the bottom, that the "turnover" aeration creates, in some cases more than twice in a 24 hr period, is still going to disturb or stir up the muck even below the raised diffusers? If not, isn't that defeating the purpose somewhat? That we want some disturbance so it can decompose, and that we want ALL the water moving?
I can understand at initial startup how it would stir things up around the diffuser but it would seem in short-order that the area around the diffusers would be cleared, so to speak (at least with a rubber membrane diffuser as I'm not familiar with the silica stones).
Is it possible to over-aerate? i.e., too much water moving or too many turnovers per day?
Just some thoughts.
