sps?

[Snappy]

I would say green or orange Montipora Digitata or M.caps as you may not have enough light for the purple to maintain a deep colour. You can go with several acros as well. There are a variety of blue tip stags like A.microphthalma that would do very well. If you're interested pm me I could recommend an excellent sps frag starter pack for you with a good mix.