DrLuke, I think it could be possible your pond suffered a turnover with all the rain you've gotten. 40 years old and unaerated, there might be some nasty stuff down there.
"Forget pounds and ounces, I'm figuring displacement!"
If we accept that: MBG(+)FGSF(=)HBG(F1)
And we surmise that: BG(>)HBG(F1) while GSF(<)HBG(F1)
Would it hold true that: HBG(F1)(+)AM500(x)q.d.(=)1.5lbGRWT?
PB answer: It depends.
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