(Bismarck, ND) -- State agriculture officials have issued a quarantine on moss balls, which are popular with fish owners because they help create oxygen in tanks and eliminate pollutants.  But moss balls from the Ukraine have been found to contain invasive zebra mussels.  The infested moss balls were found at pet stores in Bismarck and Fargo.  Zebra mussels can be destructive to native fauna.  Agriculture officials say an outbreak of zebra mussels could be devastating to North Dakota rivers and streams.