Zebra mussels found in several Wyoming pet stores

    (Cheyenne, WY) – An invasive mussel that poses a serious threat to Wyoming’s natural resources and water systems has been found in a number of pet stores across the state.

    The Wyoming Game and Fish Department has confirmed the presence of zebra mussels in “marimo balls” or “moss balls,” a product sold at many aquarium and pet supply stores.

    Game and Fish is urging anyone who has this product to carefully dispose of it and aquarium water immediately. Proper disposal is essential to help mitigate the potentially catastrophic effects mussels could have for the state.

    h/t WGFD

    “Zebra mussels are an extremely destructive aquatic invasive species,” said Game and Fish Chief of Fisheries Alan Osterland. “Once they become established in reservoirs, lakes or even city water systems, they wreak havoc. They remove nutrients from water, clog pipes and waterways, damage boats and out-compete native mussels. Further, in many cases, zebra mussels are impossible to remove and could have costly impacts for Wyoming.” 

    A marimo ball is a popular tank decoration made of a green filamentous algae used to oxygenate the water. It’s important that anyone who has purchased a marimo ball closely follow the recommended steps for disposal. 

    To dispose:

    1. Remove any pets from the water and tank.
    2. Remove the marimo ball, other plants and any water from the aquarium and put them into a heat-safe pot. Do not dispose of any water down the drain or toilet.
    3. Inspect the marimo ball and tank for zebra mussels and if you find any contact your local Game and Fish regional office or local warden.
    4. Boil the marimo balls, plants and any water it’s been in contact with for at least five minutes
    5. Dispose of the marimo ball and other plants in trash. 
    6. Pour out the boiled water on a semi-permeable surface. That could be a houseplant or outside — like grass or soil — that is not located near standing water or a storm drain.

    Do not flush the marimo ball or pour aquarium water down any drains, toilets or into nearby water sources like a local pond or creek. These actions could spread zebra mussels throughout the water system. 


    “We are urging folks to take extra precautions and please follow these disposal instructions. It’s essential for our state’s fisheries, wildlife and communities that these steps are followed. It will be key to mitigating the potential impacts Wyoming now faces,” Osterland said. 

    Anyone who finds zebra mussels in their tank must call the local Game and Fish regional office so a representative can collect the sample. Possessing any aquatic invasive species (AIS), such as zebra mussels, is illegal, and people are required to report the discovery within 48 hours.

    Zebra mussels are striped, sized less than 2-inches. They attach to any hard surfaces such as metal, glass, plastic, stone, wood or rocks. They are extremely resistant to cold temperatures and many chemicals. Hot water is the most effective way to kill them and keep them from establishing. 


    “Even if you can’t see mussels, it doesn’t mean they aren’t there,” Osterland said. “When zebra mussels are in their immature stage, called veligers, they are so small you can’t see them. But, they can grow in even tiny amounts of water. That is why it is so important for everyone to take precautions.”

    Pets and other aquatic animals are not immediately impacted by zebra mussels. 

    “Pet fish, turtles and the like should be safe; just clean your tanks and follow the disposal instructions for the plants and water,” said Osterland. “Never release your pet into the wild or pour your tank water into a natural water source. This can also spread invasive and other unwanted species.”


    Wyoming is one of several states across the US to identify zebra mussels in pet and aquarium stores in connection to marimo balls. The Department is working closely with other states and Federal agencies to address this nationwide issue. Game and Fish is urging any stores to immediately remove this product from shelves and contact their local Game and Fish office

    Zebra mussels have never been identified in a Wyoming water source. Aquatic invasive species, like zebra mussels, quagga mussels, and others, are typically transported on watercraft. Annually, Game and Fish devotes $1.3 million to the AIS prevention program, which includes inspecting and decontaminating boats entering the state and it’s waters as the first-line for defense for the protecting Wyoming. More information on the prevention of AIS is available on the Game and Fish website.  


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