Owatrol mould stop stops mould from gowing when added to mortar, paint, adhesives or grout. A few drops of Mould Killer VC175 added to the paint and your surfaces means that surfaces stay looking like new. Owatrol mould stop is a durable and strong algae and mould killer. It is long-lasting and can be added to a wide range of products such as paint, timber stains, textured coatings, grout, mortar and adhesives to prevent the formation of mould and mildew.