Government of New Brunswick

The Department of Natural Resources and Energy Development wishes to advise the public that invasive zebra mussels have been detected in a variety of moss/ algal ball products. These products are often sold as Marimo Moss Balls in pet and garden stores for aquariums and water gardens.

First reported in a U.S. pet store in early March 2021, the small freshwater mussels have since been discovered hitching a ride on moss balls in various jurisdictions including New Brunswick! While they may look inconspicuous, zebra mussels are considered to be one of the world’s worst aquatic invasive species: they multiply extremely quickly, taking over areas to the point that they damage infrastructure, clog water in-take pipes, endanger native freshwater mussel species, drastically alter ecosystem functioning, and make recreational areas like beaches unusable.

Please do your part to keep zebra mussels out of New Brunswick’s waterways.


Inspect the moss balls for tiny hard shells both outside and in the moss ball. Zebra Mussels only get about as large as a thumbnail, however they are being found at much smaller stages. Even if you do not see a zebra mussel there is still a risk that your product is contaminated as the larval stage of these mussels are invisible to the naked eye and free-floating in the water. As such, people who purchased a moss ball within the last 4 months are being encouraged to return them to the place of purchase or dispose of them responsibly.

Follow these three steps to treat and dispose of moss/algal balls:

Step 1: Treat the moss/algal balls:

  • place into a plastic bag, seal and freeze (preferably in a deep freezer) for at least 24 hours,
  • place in boiling water for at least 1 minute and then let cool.

Step 2: Dispose of moss/algal balls:

  • place it and any of its packaging in a sealed plastic bag and dispose in your household garbage.

To prevent zebra mussels from getting into our water bodies, DO NOT dispose of the moss/algal ball or any aquarium/water-garden contents (e.g., substrate, plants etc.):

  • by flushing down the toilet;
  • by putting down drain; or
  • in a compost.

Step 3: Treat aquarium contents and water

The treatments outlined below must be followed exactly as described to be effective in decontaminating tanks and systems.

Post treatment water should be disposed of through your wastewater system.

Method 1: Heat treatment for tanks without plants or animals or with plants or animals removed

This method provides a treatment option for tanks without plants or animals (either not present or removed as it may harm/damage or kill other plants or animals).

1. Raise the temperature of the water by using an aquarium heater or pouring in boiling water. It is important to maintain the temperature throughout the treatment to achieve 100% mortality of zebra mussels. Please refer to the table below.

Method 1: Heat treatment for tanks without plants or animals

Minimum temp.

Minimum time


30 min


15 min


5 min

2. Ensure all tank accessories (e.g. filter) and equipment (e.g. nets) used to remove fish, other organisms or plants from the contaminated aquarium are properly decontaminated immediately after use by using the heat treatment method above.

3. It is recommended that you monitor your tank for the next several months for any unusual or unexpected aquatic life. 

4. Water from all water changes during this period should be treated as above.

Method 2: Potassium Chloride (KCl) for tanks with plants or animals

This method can be used when plants and animal cannot be removed, or if Method 1 is not possible. While this method is considered safe for most finfish and plants, it may not be safe for invertebrates.

This treatment requires using potassium chloride (KCl), a sodium-free table salt substitute commonly sold at grocery and nutritional stores. The highest available purity of KCl available should be used.  “Half-Salt” products cannot be used.

1. Remove a small volume of water (approximately 1 litre) from your aquarium and place this water into a separate container.

2. Determine the volume of water in your aquarium and the corresponding amount of KCl required to achieve the required treatment concentration using the table below.

Method 2: Potassium Chloride (KCl) for tanks with plants or animals

Volume of Water in Aquarium

Amount of KCl Required* (100% Solubility)

US gal


Teaspoons (US)












3 ¾








13 ½




16 ½




22 ½


*Dosages outlined in this table are based on a known, lethal concentration of 100ppm KCl to invasive mussels, over an exposure period of 14 days and within the expected temperature range of home and retail aquariums (above 17 º C). Measurements in this table have been rounded up for ease of measurement.

3. Add the required amount of KCl to the separate container of water and mix thoroughly.

4. Pour the mixture back into your aquarium and leave it in for at least two weeks at a minimum temperature of 17°C.

5.  Water changes should be avoided during the 14-day treatment period. If this is not possible, treat the discharge water with Method 1 prior to disposal.

6. Evaporated water can be replenished provided the replacement water does not exceed the volume of water that evaporated.

7. To ensure consistent treatment conditions, all make-up water must be prepared using water from an uncontaminated source, warmed to a minimum of 17°C and pre-treated using KCI.

These steps apply to all tanks that have had the moss ball present even if for a short period of time; regardless of whether the moss ball was previously removed from that tank.

Step 4: Report

Report this incident to your local Aquatic Invasive Species authority and let them know that you have treated and disposed of your moss balls.  

Zebra Mussels pose a serious threat to Canada’s aquatic ecosystems, but you can help stop the spread. For more information on Zebra Mussels in Canada, please visit: