Rotenone. GS are susceptible to lower levels of Rotenone than other fish, so if you walked the fine line, you could kill the GS and not kill the rest of the fish in the pond, if that's what they are.

All it takes is 2 to get things going. If someone stocked the pond with left-over minnows a few years ago, that could be how.

I believe the local lake got them because someone less informed thought they'd help the lake out by stocking threadfin shad, which look like GS when young. Also, Threadfins won't survive our winters.

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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).