I bought a water sprite about a year ago, rather expensive ($3-4), small, and it was planted in the store's aquarium. I planted it at home and within a few days realized that it spread itself by developing small plants along the leaves. That original plant has since passed on (so to speak), but its descendents live in my two aquariums and in our pond at work (the pond being like a deep, narrow swimming pool, and work being 5 miles from the nearest waterway, and me living in the high desert, so about zero chance of the plant escaping). I've tried replanting the offspring but they always do poorly (they look unhappy & they rot away). For me, they prefer to float. I don't much like that since each plant spreads out and blocks light, and the roots flow down like brown hair, though those characteristics are okay in the pond since maybe the goldfish will eat them. The plants grow differently in the pond, too. In the aquarium they send up fern-like shoots that get to maybe 3" then die back. In the pond, which gets some sunlight, the shoots look hardier and reach 9-10". There they also compete with hyacynth, water lilies, anarcharis (which bloom there), papyarus and probably a few other things. I don't know if the water sprite (or anarcharis or papyrus) will survive the winter; I'll report on that in the spring.