Very simple arrangment but I like it

Just an idea but you could move the rocks forward a bit and then let caulerpa prolifera grow in on the sandbed behind the rockwork. Would make a nice background for the corals and help with water quality too. Caulerpa prolifera is the one that looks like seagrass and it's easy to control unlike some of the other caulerpa's....
http://www.zanclus.it/immagini/inver..._prolifera.jpg