I don't know of any pond herbicide that will only control bladderwort and not other beneficial pond plants. Triploid Grass Carp will eat it, but they will also eat other plants. You can weed razor/rake it out, but it's very labor intensive.

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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).