ALERT: Invasive zebra mussels found in aquarium moss balls across the U.S.

Share or view as webpage  |  Update preferences

ALERT: Invasive zebra mussels found in aquarium moss balls across the U.S.

Aquatic organism sellers urged to check stock immediately

The Michigan Department of Natural Resources is requesting pet stores, suppliers and hobbyists immediately check aquarium moss balls for invasive zebra mussels, a restricted species in Michigan. Under state law, zebra mussels cannot be possessed alive in Michigan, so contaminated moss ball products must be disposed of properly.

More information about zebra mussels is available at

The DNR received an alert from the U.S. Geological Survey that supplies of moss balls distributed as Mini Marimo Moss Balls (SKU 5292944) and Marimo Moss Balls (SKU 5164031) to a Petco store in Seattle, Washington were found to contain zebra mussels. An alert Petco employee noticed the mussels and filed a report to the USGS Nonindigenous Aquatic Species online reporting system.

After the alert was issued on March 3, many states across the U.S. reported finding similarly infested stock at Petco and PetSmart stores. Inspectors in Colorado have confirmed infested stock in at least one independent retail outlet. Additional infested stock may include Imagitarium Betta Buddy brands.

What to look for

zebra mussel in moss ball

Marimo moss is a rare form of algae from Northern Europe and Asia, and Marimo moss balls are a popular aquarium plant used to generate oxygen and remove nitrates from tanks.

The moss balls may be sold as large balls or separated and repackaged in smaller containers at the retail level. The balls are sometimes packaged with individual betta fish in cups or containers.

Because it is not yet clear if the infested stock is limited to a single supplier, all moss balls in stock should be inspected for zebra mussels.

What if I find zebra mussels?

In Michigan, zebra mussels are listed as restricted under Michigan's Natural Resources Environmental Protection Act (Part 413 of Act 451). This means that it is unlawful to possess, introduce, import, sell or offer that species for sale as a live organism, except under certain circumstances.

Moss ball in aquarium tank

If zebra mussels are found on any moss balls in stock or in aquariums, infested moss balls should be removed. Infested moss balls and packaging should be double bagged, sealed and disposed of in the trash.

The DNR recommends that tank water from aquariums holding infested moss balls be decontaminated by adding 1/10 cup bleach to every gallon of water and allowing at least 10 minutes of contact time before draining. 

The DNR also recommends that any other moss balls in stock be removed from shelves. Sellers should contact their suppliers to determine whether the stock may be infested. 

Report zebra mussel detections

All discoveries of zebra mussels in stock must be reported to the state.
Reports should be made to Seth Herbst, DNR Aquatic Species & Regulatory Affairs Unit Manager, at or 517-388-7759. You can also use this contact information for assistance with inspection or proper disposal.

Regularly inspect new stock

To prevent the introduction of invasive species, retailers, wholesalers and enthusiasts are encouraged to inspect and rinse new aquatic plants to rid them of seeds, plant fragments, snails, mollusks and fish. If you receive any stock that includes suspicious plants or animals, report your find at

Michigan State University Extension’s Reduce Invasive Pet and Plant Escapes (RIPPLE) program offers information and materials to help retailers and enthusiasts prevent the introduction or spread of aquatic invasive species. Learn more at