Water Wisteria (Hygrophila difformis). This plant can adapt to low light conditions and still grow fast and gorgeously. Makes a great space filler and has a beautiful white color on the under sides of the leaves. Under water it grows and has a "different" look to it, which adds variety. If allowed to grow outside the pond water such as on the surface of the water or outside an aquarium tank the leaves will take on a different shape and bloom pretty purple-blue flowers as it emerges out of the water. Very easy to grow.