SherWood, If the aeration system was running for a week or longer, you shouldn't' feel that big of a difference between bottom and top water temp. 4-5 degrees at most.

If it's greater than that, the aeration system isn't running long enough per day or it's undersized for 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).