I've often wondered about just how much damage chemicals in ponds can do. In no way am I advocating wholesale or unwise use of chemicals in ponds.
However, when I think about it, one inch of water over one acre is 27,000 gallons at approx 8 3/4 pounds per gallon. If I figure a one acre pond with an average depth of 10 ft, I come up with a big chunk of water. Do your own math. So, what damage can 6 oz of Roundup, with a surfactant thrown in, mixed in 5 gallons of water really do when sprayed on shoreline plants?
Please remember and understand: I'm not giving advice here.