My grass carps loved water hyacints - after I brought new plants, they were tearing them apart in less than 5 minutes. I've tried twice and then I got rid of grass carps in the pond - which from the beginning was wrong idea. If you are a beginner gardener, as I used to be, maybe nobody will warn you 'don't let grass carp to your sweet garden pond'. Feel warned now. And don't let them in.
Water hyacinth are a lovely floating perennial aquatic plant native to tropical and sub-tropical South America. In colder climate zones it is annual, as winters are to harsh for them to survive.
This is one of the fastest growing plants known - they double their population in two weeks! also ther seeds are known to be viable up to thirty years.
So if your winter are mild watch out - and check if water hyacinth is not invasive in your region.
If it's safe to let it to your pond, do it - maybe it will send you these lovely blooms?
This lovely blooming plant has a high capacity for uptaking of heavy metals, including Cd, Cr, Co, Ni, Pb, Hg and cyanides, which it suitable for the biocleaning of industrial wastewater.
Further recommended reading Backyard Water Gardens: How to Build, Plant & Maintain Ponds, Streams & Fountains