Duckweed is my nemesis! yes Sonar and its generics work, but for a large curvy pond like mine it is very pricey. I've had great initial results with clipper. Really took care of my submerged weeds ,but all you need is a tiny bit of duckweed to survive and it takes over the pond in a couple weeks! Now I'm just trying to keep the main fishing and swimming area clear of it. Has anyone had luck with using a strong aerator with a couple diffusers to keep the area clearer?