Roundup is not rated for aquatic use due to the surfactant (wetting agent) used in that formulation. The active ingredient, glyphosate, is found in many other herbicides (Rodeo, Aquamaster, etc). Typically these are rated for aquatic use because they lack a surfactant. The directions usually specify that you must add a "non-ionic surfactant". See http://aquanic.org/publicat/usda_rac/efs/srac/361fs.pdf

Frank

Book Owner and Magazine Subscriber 3 acre pond central GA