looks like you have 2 yellow tail damsels in there. They can be super mean fish which will limit what else you can add to the tank.
I would ditch the damsels so you can add anything you want.
with a 30 octo, did you think about a school of bangaii or pj's? That might look neat.
also, smaller isnt really easier in saltwater, just cheaper. Generally, the bigger the system you have, the easier it is to keep. This is because any fluctuations in a small tank can be deadly, while it takes a much larger fluctuation in a larger tank. And by fluctuation i mean temp changes, human errors, overfeeding, ph changes, water changes, ....
goodluck