If treating planktonic algae, then yes, you'd have to treat the whole BOW to achieve the correct PPM level. If you were spot spraying or treating an area, then just calculate for that area.

I wouldn't use CU+ for treating the whole pond at once if the bloom is moderate to heavy. Too great a risk of creating a DO sag. Phyco makes O2 as it breaks down, that is why it is used in aquaculture applications to treat the whole water volume at once. MUCH less of a risk of an O2 crash.

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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).