There are a lot of smaller robin species, though. Perhaps a marine biologist could tell you which of them are smaller? I know there's one kind that's like 6" or so at full size.
Monos and scats? That would be cool, they're neat fish.
Have you considered lookdowns as an option? I personally think they're neat. Really active, though...
Would a snowflake eel be an option? I'm not sure about their compatibility, but it seems like you're keeping mostly large-ish fish that a snowflake couldn't eat.
You should get a handful of yellowtail damsels. They kind of half-school around corals and such, and they mostly avoid the attention of larger fish from what I've seen. There's a bunch of the little guys in the touch tank I'm remembering, as well as in a shark touch tank (little sharks) and they're pretty neat. Plus, $20 should get you like 10 of them.
Sea moth?
Maybe a small flounder species? Or a ray?
I know you probably have a plan, I'm just chucking ideas at you.
What's the biggest guy you have planned? Biggest mouth?
Ooh- you should stick a couple of mangrove propagules on top of your rock islands. You could let them grow nice and huge.
Are you going for kind of a bay-type look? Like the sandbed/rock/coral areas that aren't quite reefs? Because if so, I vote for a couple big piece of driftwood.
Hey, I bet you could chuck a lot of 'pest' crabs in there. They'd either be fine (too small to kill things) or they'd be snacks.
