Forums DIY Controlling pond blanket weed? Reply To: Controlling pond blanket weed? May 21, 2018 at 2:34 pm #339 Phil 9 Posts You can reduce light with water lilies and the like. Our pond, which gets a fair bit of sun as ponds should, is covered in duckweed too which, although a pain, does do a good job of keeping the light levels down and can easily be skimmed off with a net, or hands, to control it. We have lots of oxygenating plants too and the water has remained clear and free of blanket weed year on year. No fish though.