Spaghetti leathers, devils fingers, and nepthia are some softies that sway in the current. Any Euphylla genus coral (frogspawn, torch, hammer, galaxea), bubble corals, and elegance corals (although I wouldnt reccomend an elegance) are some good LPS that sway in current. Some SPS corals get pretty furry like pocillipora, millepora, and stylophora but those are of course more difficult to keep.
Hmm, I thought posted in this thread this morning? Now I cant see it! Ohwell, LOL.
What I said before, have you seen some Macro Algae? That can look alot like grass, depending on species, and they have a wide variety of colours/textures! Also, Green Star Polyps! SHouldnt be too dear or hard to come by, and once they mat out, they can move/look grassy!