Lake Howell in Orlando, a relatively large lake, 404acres, a city sewer line broke and dumped millions of gallons of raw sewage into the lake back in the 90s... the years afterwards experienced an explosive growth of hydrilla, really itchy stuff to rub against your skin, thick and can literally grow a foot or more in warm summer water! So the county put in a large quantity of sterile young Russian carp back in the 90's in addition to spraying the shoreline hydrilla with some sort of chemical that was safe to other aquatic life in the lake.