Killing cattails is a must to keep the growth under control. The best way to kill cattails is by using an aquatic approved herbicide with the active ingredient, glyphosate. Glyphosate is the active ingredient in Round Up, but Round Up is not approved for aquatic use and could harm your fish.

How much Roundup does it take to kill cattails?

Glyphosate is a systemic herbicide which means it will kill the whole plant even if only part of the plant is sprayed. Dilute 2 2/3 ounces of 53.8 percent glyphosate in 1 gallon of water, put it in a garden sprayer and spray it evenly on the cattails.

How do you permanently get rid of cattails?

Glyphosate, while more expensive, is a more effective permanent solution since it is systemic. Systemic herbicides work their way throughout the entire plant, killing below the ground as well. Spray it liberally on visible areas of cattails one time for full effect.