I have found Curly Pondweed (Potamogeton crispus) and Creeping Primrose (Ludwigia palustris) in the pool that forms below my spillway. I don't want this in my main lake. I already have 30 pink sensation water lilies there that I want to save. I will dig an spray their roots of all soil before I attempt to kill the invaders. What exactly can I do. The pool is around 30 feet by forteen and three feet deep with 3-100 gal/min waterflow depending on rainfall. What herbicides. I would like to kill them in the fall if possible then replant waterlilies in the spring. Pool bottom is mud. In meantime I am controlling by pulling off the tops by hand.