Invasive mussels detected in aquarium moss balls

The Washington Department of Fish and Wildlife (WDFW) is asking anyone who has purchased moss balls for their aquarium to inspect the plants for invasive zebra mussels.

A mussel is shown inside a ball of moss
Photo by WDFW
Zebra mussel found in Marimo moss ball. Usually about the size of an adult fingernail, zebra mussels can be as large as two inches or as small as a sesame seed. 

In March 2021, several states reported the presence of both live and dead zebra mussels at pet store retailers nationwide. Retailers quickly acted to pull the product from shelves and place them in quarantine. The wholesale distributors out of California and Florida were notified, and shipments into the country were ceased. For more details, read the March 4, 2021 news release

Zebra mussels are a prohibited aquatic invasive species in Washington State that, if established in local waters, would be capable of causing significant infrastructure and environmental damage. 

Quagga and zebra mussels can clog pipes and mechanical systems of industrial plants, utilities, locks, and dams. If invasive mussels take hold in Washington, officials estimate it would cost more than $100 million each year to keep Washington’s power and water infrastructure running, in addition to causing catastrophic ecological damage.

How to report

WDFW and the Washington Invasive Species Council recommends that anyone who thinks their aquarium may be carrying invasive mussels to report it online using the Washington Invasives app or online reporting form. It is as easy as taking a photo and submitting for an expert to review. 

How to safely dispose of moss balls

Two methods for the aquarium owner to safely dispose of the moss ball(s):

  1. Remove the moss ball(s) and place in a plastic bag. Put the bag in the freezer and leave for at least 24 hours. After that, the moss ball(s) can be disposed of in the trash.
  2. Place moss ball(s) in boiling water for at least one full minute. After that, the moss ball(s) can be disposed of in the trash.

Aquarium species and accessories: 

Collect the fish & plants and place them in another container. Dispose of the water in a sink or toilet. All municipal wastewater is treated to kill all pathogens, and septic tanks are fully self-contained underground.  

Carefully use water that is 140 degrees to flush and coat all the tank and accessory surfaces. It is recommended that you do another water change within a week and continue to monitor the tank for any unusual aquatic growth.  

If you do not have access to high temperature water, a 1/3 cup of unscented household bleach per gallon of water can be used as a disinfectant. Allow the aquarium, substrate, rocks, décor, and filter media to soak in the bleach water solution for 10-15 minutes. After adequate contact time, thoroughly rinse off all items prior to resetting up the aquarium. When resetting up the aquarium, dispose of the previously used filter media and replace with new media. Finish by using a dechlorinating product to neutralize any residual chlorine prior to reintroducing aquatic life.

For extremely large aquariums that you may not be able to completely dewater/decontaminate, dispose of the moss ball(s) as above. Officials recommend that the public conduct frequent water changes and continue to monitor the tank for any unusual aquatic growth.