Zebra mussels have been found in Maine pet stores and state officials are asking store operators and consumers to destroy the highly invasive species.

The mussels have been found in aquatic moss balls that have been sold at pet stores in southern and central Maine and elsewhere in the United States, Maine Department of Inland Fisheries and Wildlife officials said. If released into the wild, the freshwater mollusks can quickly outcompete native species and clog boat motors, hydropower plants, intake pipes and other structures in the water.

Invasive zebra mussels have been found in moss balls sold in pet stores in southern and central Maine. Photo courtesy Maine Department of Inland Fisheries and Wildlife

State officials said they have been found in moss balls that are sold as aquarium plants. They carry the names “Beta Buddy Marimo Balls,” “Mini Marimo Moss Balls” and “Marimo Moss Ball Plant.” They are sold separately, state officials said, but are also often included in the sale of beta fish.

Consumers shouldn’t try to destroy the moss balls by flushing them down toilets or disposing of them in places where they could get into a water system. Stores are being asked to remove the moss balls from the shelves and destroy them immediately.

Officials recommend three ways to destroy the moss balls and kill the zebra mussels:

• Place them in plastic bags and freeze them for at least 24 hours

• Boil the moss balls for at least a minute

• Submerge the moss balls in chlorine bleach for at least 20 minutes

If the moss balls have already been placed in a fish tank, the tank needs to be disinfected. State officials said the fish should be removed, all aquatic plants should be disposed of by freezing or boiling and the tank disinfected by adding a cup of household bleach to each gallon of water in the tank, mixing it well and then letting it sit for at least 10 minutes in the tank. After adding the bleach and letting it sit, the disinfected water should be drained and disposed of down a sink or toilet. All other items in the tank – gravel, pumps, filters, decorations and other items — should be disinfected with a cup of bleach per gallon of water and then letting the items soak for at least 10 minutes.

Do not pour water down sinks or flush it in the toilet without disinfecting it first and don’t dump untreated tank water near any outside water body, including storm drains.

Zebra mussels are fingernail-sized mollusks native to fresh waters in Eurasia, named for the dark zig-zag stripes on their shells. They are believed to have arrived in the U.S. in the 1980s, probably in ballast water in ships from Europe that was discharged into the Great Lakes.

Before the mollusks were discovered in moss balls, zebra mollusks have not been found in Maine.

They reproduce rapidly, forming dense beds on lake bottoms and hard surfaces, including the shells of native mussels. Zebra mussels eat by filtering out algae and other nutrients that other freshwater mollusks and fish need for food. 

Zebra mussels are a restricted or prohibited species in Maine.

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