I would suggest if you are going with a 5.5 G and 24 watts of PC to go with alot of your soft corals. Zoanthids, mushrooms, polyps will all be nice and spread to cover most of the rocks. You might want to also look into some of the LPS such as some of the candy-canes, trumpets, or maybe an open brain. If you go will some of the soft corals they will outgrow the tank very quickly if they are happy such as leathers, and colt corals, kenya trees and such. I will try and get a pic of my old 2.5 covered in mushrooms and some others up in the next bit, with just 18w of PC light and a HOB filter.