Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Submerged weeping willow eradication.

With the Grazon PD, go to the label, open it and read the first paragraph of the Environmental Hazards. That should answer the question for that herbicide.

Do the same with the KillzAll and see what it says. Basically, the label is the law, so if it's not specifically recommended for aquatic use, no one will recommend it to be used in a way that isn't in accordance to the label.