Cecil, if your overflow drain in that pond takes water from the top, I think you might lower the temps a bit more by not using the bottom diffuser, and adding the water to the bottom of the pond. The warmest water will stay on the top, and be the first water to go out thru the overflow pipe.

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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).