[racer]

Water quality has indeed been improved in the Great Lakes since the introduction of zebra muscles in the mid 80's. The down side that is frequently missed by those who equate clear water with water quality is the very rapid growth of these invaders on city water intakes and powerlant intakes. In some cases plants had to be shut down so that intakes could be cleaned. In addition, anyone who has been to a Great Lake beach knows that now bathers need to wear protective footwear to guard against the very nasty cuts caused by stepping on hard surfaces such as rocks and other freshwater bivalves that are infested with zebra muscles. After reading the first post in this thread I find it somewhat curious that anyone could make the case that zebra muscles do no harm.