If money and terrain permit, to remove the muck you'd be better off dropping the water level and digging it out. Either with an excavator or a drag line. Using aeration and bacteria will take years for a partial reduction. Exactly how fast it breaks down is a "it all depends" situation.

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).