Go take your bottle of cattail killer and flip it to ingredients and do the same with the round up. Same thing but your paying twice as much for the cattail killer. I don't use round up anymore either I get the generic glyphosate from the big R store. And I am really carfull with it. I don't do the whole pond I do it in areas in serveral weeks. I learned this from someone that does it for a living. Round up is way over priced too. I am not saying go dump a gallon of glyposate in your pond. I think it is 3 1/2 ounces per gallon of water in a sprayer. I even add a couple drops of dove soap to help see where I hit. And I try to get it on the cattials only. So what hits the water is very minimum.