Weeds like this restrict the flow of wind and sun light and will cause you problem with your lagoon working like it should. Wastewater in the lagoon is treated by bacteria, algae, sunlight, and wind. If cattails get into the lagoon, there are chemicals that will kill them, but they must be pulled out by the roots. The best way to avoid cattails is to keep plenty of water in the lagoon. Duckweed is another plant that can interfere with lagoon operation and can be killed by the same chemical herbicides as the cattails.
