Water Hyacinth...Pretty Pet Plant Or Pest?

Some states have banned importing or selling this extremely invasive floating water plant, and most fishermen hate it because it clogs their lines and hinders navigation. In my water gardens it grows and multiplies so fast I have to continually pull out thickets of it to keep it under control. Its roots are wonderful filters and keep the water clear, and when it sends up flower stalks like the one in this photo, I enjoy it.