Question
The water hyacinth in our pond garden in the Minneapolis MN area are getting black spots year after year and I don't know how to get rid of it without harming goldfish.  Any ideas?

Answer
Hi Ginny,
Thanx for your question.  The black spot is most likely a fungal infection.  I know of no methods for getting rid of it without endangering your gold fish.  You might try removing the plants that are diseased but most likely the pathogen is in the water too or begin spread from the fish or snails or other plants.  When you introdcue new water hyacinth in the pond make sure they are disease free.  Waterlily aphids can cause discoloration too.  Look for tiny crawling dots.  I'm not a watergardening expert so you may want to check over in that forum too.  I hope this helps.
Tom