RobertB - Yes. I fixed the bacteria thing above; proof reading error. As you mention, ponds with high BOB do require more water movement to minimize oxygen drops to the low levels. In our area we deal with mostly ponds less than 1 acre and fairly new systems which typically have relatively low overall BOD. Organic rich, shaded ponds, and large ponds do require different aeration periods.
Turnover rates are basically determined by testing. Theory often carries little weight here.
In my understanding of organic sediment decompositon, the invertebrates such as midge larvae, nematodes and oligochates play a very big part in the deep water detritus processing. All these guys also require DO levels at the mud sediment interface. Bacteria are responsible for the final stages of decay to chemical products; DOC's (dissolved organic carbon) and other complex by products..
Did your shatttered vanes occur mostly in cold weather or winter? I will call an engineer that helps me with problems at Gast Mfg next week and report back.
