If it is Southern Watergrass, the information says that it can form dense colonies. Control is with glyphosate based products or fluridone. I think it would provide good cover for small YOY fish and invertebrates if it didn't get too dense.

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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).