Hydrothol 191 - Contact Herbicide and Algaecide 

Hydrothol Granular with alkylamine endothall is a selective, rapid-acting, contact herbicide and algaecide. Controls submersed weeds and algae in lakes, ponds, irrigation canals, and drainage ditches. Works rapidly enough to be effective in both still and slow moving water. May be harmful to fish at recommended application rates.More- http://www.killlakeweeds.com/products/hydrothol-granular