I spy with my little eye… a very tiny mussel that causes very BIG problems! Moss balls are a popular addition to fish tanks across the country and are generally harmless on their own. However, they can sometimes harbor an unwanted hitchhiker: the injurious zebra mussel. Native to eastern Europe and Russia, but invasive elsewhere, zebra mussels were first detected in the United States in the late 1980s and have spread rapidly throughout many rivers, lakes and reservoirs across the country. These mussels attach to hard surfaces in dense colonies, clogging water intake pipes, damaging infrastructure and outcompeting native aquatic species. Because of the many issues that zebra mussels cause, they are also considered an injurious species, and any shipments of moss balls that are found to contain zebra mussels are not allowed into the United States. Anyone who discovers zebra mussels in their moss balls should contact their state wildlife authorities to ensure compliance with any local i...