I'd use a bigger outlet, but move some dirt to make it higher to impound a wee bit more water. Maybe 12" dia? It all depends on the goals of how big of a fish you want to "stock" in there when the water rises. 6" is big for a BG, but small for a common carp.

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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).