Marimo moss balls sold at pet stores have been found to be contaminated with Zebra mussels.

Invasive zebra mussels found in Petcos in Coeur d'Alene, Washington, nationwide

Zebra mussels found in moss balls shipped to pet stores in several states, including North Dakota

Conservation Officer Service - UPDATE The Conservation Officer Service can confirm zebra mussels have been found on moss balls in Terrace. CO's collected the contaminated moss balls today, after a woman

B.C. collects thousands of contaminated aquarium moss balls - North Delta Reporter

Invasive Zebra Mussels Reported in Marimo Moss Balls - AS Magazine

Marimo - Wikipedia

Invasive mussels found in products sold at South Carolina pet supply stores

Aquarium Moss Balls and Zebra Mussels

3 Utah PetSmart locations halt fish sales out of concern for zebra mussels

Invasive zebra mussels found hiding in aquarium plants for sale at pet stores - Natural Resources

Invasive zebra mussels found in aquarium moss products

Invasive Zebra Mussels Reported in Marimo Moss Balls - AS Magazine