Several years ago I had a longnose butterfly (forcipiger longirostris) that did very well in my 90 reef - but the tank was well established and had a HUGE pod population......what was SO very cool was to watch him feed on the pods in the liverock crevices/holes. He seemed just as comfortable upside down or sideways while he nipped scuds all day......he'd do 360's while he scoured the liverock all day, and seemed very happy.....He totally ignored my lps/sps collection.
I have just purchased another one, and he is in Q tank till march 1, then he will go into that same 90, but it only has a few of the corals as the setup I had in 2004. There are a couple lps/sps in that tank now, as well as peppermint/skunk cleaner shrimp - and I have little worries that he'll bother anything but all the scuds living in/on liverock.