Pond coating is a term used to describe the layer of organic material that forms on the surface of a pond. This layer is composed of SCUM, which is a thin film of organic matter, and ALGAE, which are small aquatic plants. Both SCUM and ALGAE can be detrimental to the health of a pond, as they can block sunlight and reduce oxygen levels. Therefore, it is important to keep the pond coating in check by regularly removing any excess organic material.