Hi Chris - I have lots of gorgonians, mushrooms, some caulerpa. Lots of snails to eat the leftover food (and believe me, there will be a lot of leftovers for them to eat). I have one finger leather in there ....
The main thing is to be aware of anything that might sting or cut the little guys. And I don't have any crabs in there . ..
If you are going to put any pipefish in there . . . they HATE shrimp. Mine used to beat up the peppermint shrimps - and they WON!
I am really happy to see that you are doing your homework on these guys.
Paula