I have been offered a lot of hardy water lilies but am unsure if I should accept them. I need them to provide sun protection for an algae prone pond. The problem is, the donor pond has milfoil! I REALLY don't want to import milfoil into my pond. Is there any way that I can cleanse the lilies? Chlorine dip? I also wouldn't want to risk frog eggs coming my way. Advice, please.