From the Indiana Department of Natural Resources:
Zebra mussels, which are an aquatic invasive species, have been found in Marimo moss balls, a product sold at many aquarium and pet supply stores.
Zebra mussels have the potential to harm Indiana’s aquatic environment. They are identifiable by the light and dark stripes on their shells, which look like the stripes on a zebra.
These mussels can be tiny and are easily overlooked. If you have purchased Marimo moss balls from any aquarium or pet supply store this year, destroy the moss balls, dispose of them in the trash, and clean your aquarium. Complete instructions are at fws.gov/fisheries/ANS/zebra-mussel-disposal.html.
In addition, email AIS@dnr.IN.gov with the source of the moss balls, the approximate date of purchase, and photographs of zebra mussels on the moss balls.
DNR is working with aquarium and pet supply stores to remove and properly destroy all affected inventory.
For more information on zebra mussels or other aquatic invasive species, see dnr.IN.gov/6348.htm.