Round up Max works good if used with a surfactant or a few drops per gallon of Dawn dish soap works good to to make it stick. We checked the LD 50 on Round UP and the straight mixing dosage is max dosage on blue gills, but once it is diluted in the pond is safe under any environmental laws. It does help speed up the process if you can cut the stalks where the Round up can get in better. If not it takes about a month to kill the cattails. Rodeo is the same as Round up but you pay a lot more.