I ask the same last yr and a guy responded to use karmex. Its pricey, but works real good. Iv gotta hit my pond with it again when i get hm
In the state of texas Karmex is a federal offense. Feed stores sale it for herbicide use. But will tell you thats what to put in it. 35.65 in lufkin. It will kill you're fish and drop the oxygen level to fast. But works. As far as copper sulfate a water bottle full is supposed to kill fish and we put the whole bottle in ours and didn't kill any fish. As for as weeds it will not kill weeds. it is mainly an algecide.
