I have nothing to sell you and I am not an expert but I do have a few observations/questions that may help. Plus I can't sleep tonight grin

The "muck" is made up of how much organic material? Beneficial Bacterias, like the brands you mentioned, only work on organic materials. So, if most of your "muck" was made up of inorganic materials, beneficial bacteria would be a waste of your money.

If I'm viewing the picture correctly there seems to be a good slope. Is that correct? How old is the pond?