If your object is to have something that will use up extra nutrients, I think they would do the trick. Just try and pull them out right before or after the first frost or they'll add to the nutrient load when they die.

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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).