Cleth works sloooow, and is most effective on young plants. You'll think it isn't working then all of a sudden realize the grass is gone. I've never used it on the pond edge though so no real help there. I believe the label says "slightly" toxic to fish. Take this with a grain of salt but in today's world of covering your own butt I think they label food as slightly toxic.

19 acre watershed pond
LMB, BC/WC, Bluegill, Crawfish, GShiners