Thanks for this interesting thread, folks. My method is not very scientific, but I can contribute a bit of experience. I used one powdered microbe mix for three years, and switched to another this year. I have noticed a significant improvement in both clarity and (crossing my fingers, knocking on wood) lack of fil. algae this year since I started using them. Of course, it's still only mid-June, but we have had a batch of 85-90 degree days and I expected more algae than I've observed. I am also pleased with what seems to be a decline in bottom sludge, although I can't fathom any way to evaluate that except by feel and smell, so it's totally subjective.
Further diluting the observations, I did use an enzyme slurry one time at the beginning of the summer, just for fun, and don't know whether that contributed or not--but anyway, on the whole, the current microbe treatment seems to be making a difference.
It also appears that the Aquamats I put in three and four years ago are behaving more as advertised than previously; each has a nice circle of algae at the surface. I'm willing tentatively to give the microbes credit for this performance improvement, as the Aquamat folks stress microbial treatment as part of their recommended regimen.
That said, the expense of using microbes in a bunch of ponds or a big pond would be extremely prohibitive.
