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Moss Balls & Zebra Mussels

During the start of this year, the U.S Geological Survey (USGS) was informed of moss balls being sold in pet stores infested with zebra mussels. The U.S Fish & Wildlife Service has issued requests that any infested moss balls be destroyed and discarded appropriately.


Introduction to Zebra Mussels

Amy Benson - U.S. Geological Survey

Scientific Name: Dreissena polymorpha (Pallas, 1771)

Size: < 50 mm

Native Range: Black, Caspian & Azov Seas

Zebra mussels are small bivalve invertebrates named for their stripped shells although color patterns may vary. They are a sessile invertebrate and are mostly found attached to surfaces and objects. Mussels attach by means of threads extending from underneath the shell.


Fertilization of eggs occur in the water column. The eggs are released and fertilized in spring or summer depending on the temperature of the water. Females reach the age to reproduce at two years. After the eggs are fertilized, the larvae (veligers) emerge within 3 to 5 days and are free-swimming for up to a month.


Zebra mussels are thought to have been introduced when ballast water from a single cargo ship coming in from the black sea was discharged. Its rapid dispersal throughout the Great Lakes and major river systems was due to the passive drifting of the larval stage (the free-floating or "pelagic" veliger), and its ability to attach to boats navigating these lakes and rivers. Slowly but surely is now common in the Great Lakes region.


Zebra mussels can quickly take over once they get established in a waterbody and cause significant damage including disrupting the food chain, changing the chemistry of the water (which can cause more blue green algae outbreaks or offensive taste), and clogging water intake and delivery systems. The concern is that live mussels released into a storm drain or flushed could be introduced into a waterway.


Moss Ball Contamination

It was discovered that moss balls containing these invasive zebra mussels were being sold in aquarium and pet stores.

The US Fish and Wildlife Service issued an article explaining the situation and how to deal with it in case you have contaminated moss balls.

If you have purchased moss balls after February 1st, 2021, it is most likely they are contaminated and will need to follow the steps below.

What is a moss ball?

Moss balls are a type of algae found in fast flowing streams in Japan which tumble and compact into a ball shape. A very easy to maintain and popular plant in the aquarium hobby. They are known to be nitrate sponges.

Safe Disposal

It is common knowledge you should never release any aquatic/semi-aquatic animal or plant into your local waterways as this can dramatically affect the local ecosystems. Any contaminated moss balls must be destroyed, sealed and disposed in the trash. There are three ways of destroying the moss balls:

  • Freeze - Place the moss ball into a sealable plastic bag and freeze for at least 24 hours.

  • Boil - Place the moss ball in boiling water for at least 1 full minute.

  • Bleach / Vinegar - Submerge the moss ball in regular, unscented bleach, diluted to 1/3 cup per gallon of water, for 10 minutes; or undiluted white vinegar for 20 minutes.

Once destroyed, seal the moss balls and any packaging such as bags or cups in a plastic bag and dispose off in the trash. If you used vinegar, boiling water or bleach you can drain it down the household drain as long as it is not the storm drain where it can be discharged into the local waterways.

If the moss balls were in your aquarium please follow the directions in this updated article by the US Fish and Wildlife Service for more guidance,

Please feel free to reach out to us with any questions, comments or concerns at and we will be more than happy to help!


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