If you aerate, and will be feeding the trout during the winter in the open water, I think you should be fine with between 50 and 100 pounds of trout, providing your pond isn't at maximum carrying capacity. There's threads in the archives on carrying capacity.

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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).