I'm sure it would float just fine if it wasn't rooted but mine is rooted. It's rooted on the right side of the tank and it grows toward the light. So it's snaking up and to the middle. Tango really likes resting in it. And Huey sleeps in the top of the wisteria in his tank. It's also good for bubble nests. Or at least Tango thinks so. :D
I've taken a TON off of it to put into other tanks so it's branching like mad. Every wisteria I have in all my other tanks came from this one. It seems to do fine in hard water. I have a 15 watt Nutrigrow bulb and eco-complete substrate.