Your aquarium may be contaminated, how Washington wants you to react

Millions of dollars have been spent to prevent invasive species from reaching Washington’s waterways, but an item sold at Petco is sounding alarms that the work could be derailed by a simple item meant for people’s aquariums.

Mere weeks after Washington’s “Invasive Species Awareness Week,” the Washington Department of Fish and Wildlife is warning that zebra mussels have been identified in “moss balls” sold at stores in our state.

Zebra mussels -- also called quagga mussels -- are a small, invasive species that can spread rapidly. They are an especially large problem for Washington because they’re capable of blocking water pipes on hydroelectric dams. Some have estimated that if the invasive species takes hold, it could cause up to $100 million worth of damage every year -- repairs that would be needed to be funded to ensure basic infrastructure needs are met.

“No one organization can solve the invasive species problem alone,” said WDFW Police Captain Eric Anderson. “We are working in partnership with industry, and every level of government to solve this as quickly as possible.”


The items in question were being sold at both Petco and PetSmart, according to WDFW. “Marimo aquarium moss balls” have since been pulled from shelves -- but they were sold across the country.

If you’re concerned about the product, DO NOT simply flush them or throw them out. Specific cleaning measures must be taken to prevent the spread of this particular invasive species.

Here’s the two approved methods as described by WDFW on disposing the moss balls. Note the extended instructions below on how to handle cleaning your tank, water, etc.

  1. Remove the moss ball(s) and place in a plastic bag. Put the bag in the freezer and leave for at least 24 hours. After that, the moss ball(s) can be disposed of in the trash.
  2. Place moss ball(s) in boiling water for at least one full minute. After that, the moss ball(s) can be disposed of in the trash.

WDFW instruction on cleaning aquariums and/or equipment:

Collect the fish and plants and place them in another container. Dispose of the water in a sink or toilet. All municipal wastewater is treated to kill all viruses, and septic tanks are fully self-contained underground.

Carefully use water that is 140 degrees F to flush and coat all the tank and accessory surfaces. It is recommended that you do another water change within a week and continue to monitor the tank for any unusual aquatic growth.

If you do not have access to high-temperature water, 1/3 cup of unscented household bleach per gallon of water can be used as a disinfectant. Allow the aquarium, substrate, rocks, décor, and filter media to soak in the bleach water solution for 10-15 minutes. After adequate contact time, thoroughly rinse off all items before setting up the aquarium again. When setting up the aquarium, dispose of the previously-used filter media and replace with new media. Finish by using a dechlorinating product to neutralize any residual chlorine before reintroducing aquatic life.

For extremely large aquariums that you may not be able to completely dewater/decontaminate, dispose of the moss ball(s) as above. Officials recommend that the public conduct frequent water changes and continue to monitor tanks for any unusual aquatic growth.