Yes, it does spread rapidly. I would be afraid to put it into a mud bottomed pond. I planted some blue betony along the edge of my pond and it started spreading everywhere, under rock even to cross a barrier. I had to work like a son of a gun to get it all dug out. Also in my pond I fight algae all summer long and it hangs around anything growing like lilies or water celery. Makes a terrible mess and I can't get it out of the plants. I put Algaway 5.4 and barley in to try to keep it down in the little stream that ends in a falls.
