For years, British Columbia conservation officers have been checking boats coming into the province for invasive zebra mussels, but now it turns out they're coming through local pet stores.
The B.C. government says conservation officers inspected 600 retail aquatic pet and plant stores over the weekend and found the mussels in moss balls at "multiple locations."
The government says in a release that the moss balls are species of green algae purchased by people with aquariums to help improve water quality.
Zebra mussels pose a major threat to B.C. waterways and their rapid expansion crowds out other wildlife and damages ecosystems, pipes and infrastructure.
The government says the moss balls can be disposed of by putting them in a sealed plastic bag and freezing them for 24 hours or in boiling water for at least a minute.
After that, the balls can be thrown in the trash, never flushed or composted, while the aquarium water will also need to be sterilized before it's tossed down the drain.