Found this guy hiding behind the pump for the skimmer. We'd seen him elsewhere in holes in the live rock, with just tentacles hanging out.
What do people think? He's apparently a detrivore, but we've only found him on Japanese sites so far. Apparently, it's local to this area, and was listed as being findable in the Kagoshima area.
I got stabbed by him today,

(no ill effects, but had to pull the spines out with tweezers) so he's not terribly comfortable to handle, but other than that, he doesn't seem to be hurting anything. I did see a tank at LFS today that was crawling with them to no ill effect as well.
I assume Harlequin shrimp won't eat these right? I'm planning on getting a couple of them for my next tank project, but want to keep a species of starfish as a detrivore (and was thinking these might fill that nitch) While I'm on the topic, will Harlequins tolerate other shrimp, or only in an extremely large tank? I have a couple of peppermints that I'm rather fond of, and want to know if these need to be separate from the harlequins.