CASPER — An invasive mussel that wildlife officials have been trying to keep out of Wyoming waters has been found in four pet stores across the state, a Wyoming Game and Fish Department official said Friday.

Zebra mussels have been found in “marimo balls” or “moss balls,” which are typically sold as a decoration at pet supply and aquarium stores, explained Game and Fish Chief of Fisheries Alan Osterland.

Wildlife authorities have long sought to keep the invasive zebra mussel, which can cause major problems to native ecosystems and infrastructure, out of Wyoming, setting up boat-inspection sites at places like Alcova and Glendo reservoirs.

But they learned only this week that the mussels have been found in marimo balls on shelves in Wyoming stores.

“No one certainly saw this potential vector, but this is potentially more serious than watercraft for sure,” Osterland told the Star-Tribune.

Officials are concerned the mussels could end up in water treatment systems, lakes and rivers if an aquarium owner disposes of tank water by dumping it down the drain or flushing it down the toilet.

“Zebra mussels are an extremely destructive aquatic invasive species,” Osterland said. “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.”

Marimo balls are made of a green filamentous algae that’s used to oxygenate the water. The products come from southern Russia and Ukraine — where zebra mussels are common.

The department is urging anyone who has “marimo balls” in their aquariums to carefully dispose of them and the aquarium water.

Adult zebra mussels are striped and typically under 2 inches in size. They can attach to hard surfaces and the department says they are extremely resistant to cold and many chemicals.

“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.”

The mussels have never been identified in a Wyoming water source, but wildlife officials continue to look for them. Game and Fish spends $1.3 million annually on a program to prevent aquatic invasive species from taking hold in Wyoming through efforts like inspecting and decontaminating boats, according to the agency.

However, Osterland said it was only Wednesday when he learned that the invasive mussels have been found in Wyoming via pet stores.

“This is a national deal,” he said. “All states and the federal government are getting involved in this. The biggest thing is to stop the distribution and remove it from tanks. This is a top priority for the department right now.”

Game and Fish said these steps should be followed to properly dispose of a marimo ball:

Remove any pets from the water and tank.

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.

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.

Boil the marimo balls, plants and any water it’s been in contact with for at least five minutes

Dispose of the marimo ball and other plants in trash.

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.

Aquarium water should not be poured down the drain or flushed down the toilet.

“We are urging folks to take extra precautions and please follow these disposal instructions,” Osterland said. “It’s essential for our state’s fisheries, wildlife and communities that these steps are followed.”

Aquarium owners who find zebra mussels in their tank must call Game and Fish so a sample can be collected.