What is that pond scum type substance in my pond/lake and how do I get rid of it?
Usually lemna, or duck weed, is mistaken for pond scum. Lemna is one of the smallest flowering plants, and so a large accumulation can have the appearance of being scum-like. Actually, duck weed is very important to an aquatic community. Not only does it provide food, shelter, and protection for wildlife, but it also removes phosphates and nitrogen compounds from the water it floats on. This is how duck weed obtains the nutrients necessary for growth. There really is no easy way to eliminate lemna. The best way would be to discontinue the use of fertilizers, which are considerable contributors of nitrates and phosphates. Other ways include skimming the duck weed off the top of the water body (which in some cases can then be used as feed or fertilizer), draining or dredging the lake, or using a chemical application. These last two methods are extremely drastic however and could have severe effects on water quality. Pond ‘scum’ is usually a form of freshwater algae that creates a layer o
