Have you thought about adding a couple of feeders to feed the BG? I may be wrong (don't have any experience with Southern Ponds) but personally I'd rather try that first before adding Gizzards. You'd be feeding the LMB indirectly by feeding the BG.

Have you done any WR studies on the LMB of the different age classes?

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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).