With visibility at 12" I don't know if I'd fertilize at all. What was the clarity before the fertilization and what is your alkalinity?

Smartweed doesn't put much if any O2 in the pond. Are there any other underwater plants in 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).