Could be the underwater plants dying off, freeing up nutrients for phytoplankton. You have to determine whether the "murkiness" is due to growing phytoplankton or suspended clay. They are different and are an indicator of different things. AND are treated differently.

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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).