I've only ever seen them in the wild. Friends of mine have them with mixed reviews.
They complain that they get too big (tall). I guess they grow pretty quick with the right conditions.
They bury the roots in the sand of the refugium with the tops above the water line.
Moby
My LFS is trying them out but nobody has purchased any. They will get big if they do well and they grow above the water so if they do well, you will have to get the hedger out!