Fanwort is a common plant used for design in aquariums. Since people who have aquariums need to clean it, they go the near by ponds or drains and dump the fanwort and then it starts to spread. and that is how it invades new areas of water. with plant has roots like a weed does, so then it ends up killing the other plants and the fish ends up without food.
This plant is harmful to humans and people. Fish can get caught in the plants stems. This can cause them to die. The fanwort has really long stems and this blocks out sun light for other plants native there. This plant is expensive because if it gets stuck in the boats motar this can cost lots of money to fix. Also the government used $600 to stop the spread!