The well shouldn't be pulling any air out of the ground, and there isn't any air in ground water. What might be happening is the water that is flowing thru the PVC is creating a vaccum, and if the pipes aren't glued together, it might be sucking in a little bit of air. That little bit of air won't make any noticeable dissolved O2 change.

One acre is 43,560 square feet. IIRC Bob said that in a typical fishing pond, you'd want cover to equal 20% of the surface acreage.

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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).