The definition of a weed is a plant growing where you don't want it to grow. One persons weed might be the next persons flower. Like a broken record, without proper ID it's almost impossible to say what is the correct herbicide/algaecide. There are "broad spectrum" herbicides that nuke everything, but why "throw the baby out with the bath water" so to speak? You really need beneficial plants in the pond, so just treat the ones that are being a pain in the you know what. To do that we need a good close up picture, or a plant ID to say what is best to use.

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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).