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Zebra mussel

Dreissena polymorpha


common aquarium moss ball

Zebra mussels are an exotic invasive species native to Southeastern Europe. Zebra mussels are a small shellfish with triangular, brownish shells. As their name implies, they often have zebra-like stripes. They typically grow no bigger than an inch in size and some found in the pet store plants are less than a quarter of an inch long. This species is considered one of the most impactful invasive species in the United States. Zebra mussels have three life stages – larval, juvenile, and adult. In the larval stage, the mussels live freely in the water column, allowing them to be easily transported. Adult zebra mussels can stay alive for several days outside of water and are common hitchhikers on boats, fishing equipment and aquarium plants.

In March 2021, the FWC was informed that moss balls imported into Florida for the aquarium trade were contaminated with zebra mussels and their microscopic larvae.  Zebra mussels and their microscopic larvae have been found in a species of aquarium plants known as “moss balls” that are being sold in some pet stores under a variety of names throughout parts of the United States, including Florida. The moss balls are up to a few inches in diameter and are sold separately as an aquarium plant or may be provided with a fish being sold. Because the larvae might not be noticeable in the aquarium material, any purchased moss balls can contain zebra mussels or their larvae. 

The FWC is working with state and federal partners to address this national issue.  

Potential Impacts

Zebra mussels on shell

Zebra mussels are considered one of the most troublesome invasive species in North America. They clog pipelines used for water filtration, render beaches unusable and damage boats. They also can have harmful effects on native aquatic organisms. These filter feeders will outcompete other native species in infesting rivers and lakes. The waste they produce accumulates and degrades the environment, using up oxygen, making the water acidic and producing toxic byproducts.

How to Decontaminate Your Aquarium

Aquarium owners are urged to stop buying this product and to safely dispose of any that have already been purchased.  If you have recently purchased moss balls please follow the USFWS instructions to decontaminate your aquarium.

Remember, you should never dump aquarium materials into our Florida waterways. 

  • Don’t let your aquarium animals loose!
  • Because aquarium water may also harbor invasive species larvae, such as zebra or quagga mussels, do not dump aquarium water into Florida waterways. Dispose of tank water on the ground away from any waterways or water bodies. 
  • Aquarium plants can also be highly invasive. If you want to dispose of aquatic plants, let them dry and dispose of them in the garbage.

Frequently Asked Questions

How will I know if the moss balls I purchased have zebra mussels?

If you still have the packaging you purchased, see if the source of the moss ball is from out of country. If it is, contact your distributor to find out if your purchase may be the species of moss ball that may be contaminated. 

Will I be able to identify the zebra mussels?

Zebra mussel larvae are incredibly small and may not be visible to the naked eye. If you purchased moss balls that were imported from out of country recently, it is possible that your aquarium material has been contaminated.  Larger zebra mussel shells have distinctive light and dark bands.

 Have zebra mussels been reported in the wild in Florida/Are they established yet in Florida?

No, zebra mussels have not established in Florida.

Are there other native species that resemble zebra mussels in Florida?

Yes, Florida has many species of mussels that are native to only Florida. At least one of them, the dark Falsemussel, has stripes, has a shape similar to zebra mussels, and attaches to hard surfaces via strong byssal threads.

How else can zebra or quagga mussels come into Florida?

Zebra mussels and quagga mussels can enter Florida from other states where they have been found by being transported on or in boat hulls, on or in boat motors, and on boat trailers.  Nearly microscopic zebra mussel and quagga mussel larvae have been found in bilge water and bait wells of boats.  Boats motors and trailers of boats trailered into Florida should be inspected closely to ensure that no zebra or quagga mussels are attached. Bilges and bait wells of boats trailered into Florida should be sanitized using the same methods used for sanitizing aquariums.