Nice looking light set-up!!
I agree - frogspawn is great. It provides lots of color and movement in the tank. Got powerheads? My frogspawn are in low to medium flow and they have quadrupled in size over 14 months' time.The clownfish calls one of them home and defends his territory with a passion. As the frogspawn grows, you may want to frag some of it to trade for something else or sell to recoup some of your original cost. Think I paid about $45 for mine originally.
Green star polyps will grow over your rocks like carpet and provide movement as well. When it gets as big as you want, fragging it is super easy. You basically just tear it apart.
You might also consider some trumpet coral. It is every bit as easy to care for. There are several leather corals that are easy to care for as well, but you would want to make sure the MH isn't too much for them - may take a little research on that part.