Are things like duckweed, etc., considered algae? I have something completely covering a couple of my inground stocktank watergardens. It's a bit different than duckweed. I scoop it out occasionally (maybe 75% of it), but it comes back within days. In my underground stock tank watergarden situation, it seems to actually keep the water clearer. I don't have fish.....just tadpoles/frogs, etc. I read that it removes oxygen from the water, but if it seems to keep the water clearer, is that what's really going on? Can you have clear water with less oxygen? Anyhow........to my reason for this post..........If this stuff is covering the water over my waterlily.......will it hinder the growth of the lily? I have about 4 lily leaves floating in the mass of "algae" cover. Will it really be bad for the lily, unless I clean all of this algae/plant out? Thanks!