kill

They are an invasive species in lots of states and I would like to know how to kill them quickly (if the state recommends it, like in Florida).

i found alot of this rock in my garden which im guessing is slate but not sure and it had patches of black stuff on it which i think is tar i have sterilised the rock/slate and scraped as much of the black stuff of as possible i have put it in my tank but i have no fish in the tank yet and am...