If there are no open water sources going to the pond you can run a few strands of electric fence wire 100% around the pond close to the ground up to about 12"-18" high and 4"-6" apart. That will keep them out.

There are solar fence chargers that you can buy for less than $100. A fence that short can be easily stepped over by a human. I'd turn it off before doing so just in case.......

www.hoosierpondpros.com

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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).