Nope, has no roots just floats about on the top of the tank, unless you tie it down with something, like a hair net or nylon.
It dies off if it gets insufficient light, so if you have too big a wad of it tied to something, the stuff underneath usually goes yellow and mushy and dies off - very messy.
And if you try and trim or mow it you will end up with a mess that takes ages to try and net out of the tank :evil: