Cooler water won't help much if there isn't any O2 in it. I know it's hard to find an O2 meter but see if you can find someone nearby that has one and measure the O2 levels at the different depths. I really don't like to see less than 6mg/l in the areas of least O2.

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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).