When you do the core, make sure you take it out past the pond basin and tie it into good soil.

What are you going to use to compact the clay? I'm assuming that you will be digging down to clay and using it to "plate" over the non-clay soil that is near the surface around the edges of the pond?

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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).