C Amazing weed Water hyacinth...invasive in waterways and we
in Zone 7 or less can't keep even one.
In India and other hot countries it's used as a filtration system for human
sewage...

That is why they are so good for our ponds....they really clean them up and
starve out the algea....The algea is caused by sunlight and fish poop....take
away the fertilizer and PRESTO clear clean ponds Jerri

http://www.fringeweb.com/Ponds/JerrisPond