Copper compounds are toxic to fish and must be used with extreme care. Because copper does not break down and can accumulate in sediments, Ecology requires sediments to be tested for copper before a permit can be issued for copper application. By policy, Ecology no longer issues permits for copper use in waterbodies that have salmonid populations. Advantages Aquatic herbicide application can be less expensive than other aquatic plant control methods. Aquatic herbicides are easily applied around docks and underwater obstructions.
Some herbicides have swimming, drinking, fishing, irrigation, and water use restrictions.
Herbicide use may have unwanted impacts to people who use the water and to the environment. Non-targeted plants as well as nuisance plants may be controlled or killed by some herbicides. Depending on the herbicide used, it may take several days to weeks or several treatments during a growing season before the herbicide controls or kills treated plants. Rapid-acting herbicides like Aquathol may cause low oxygen conditions to develop as plants decompose. Low oxygen can cause fish kills.