Having trouble identifying this Acro hitchhiking crab     1/14/17
Hi!
<Hey Daniel>
I recently bought a small Acro colony and it had 3 crabs.
<Neat! Evidence of good handling>
I knew there was one in the colony, it's part of why I chose it. But I didn't expect 3! This album contains the pictures I'm referencing, feel free to host them on your site though https://imgur.com/a/5b3LK I was able to identify the small one (3rd & 4th pictures) as a Hairy blue-eyed Acro crab (Cymo andreossyi) which as I understand it will pick on
polyps.
<All will/do to extents. I'd keep them all... not that damaging in most circumstances>
On large colonies they're supposedly symbiotic, but dangerous to small colonies, so I tossed him in with my P. ciliata mantis shrimp. I was able to identify the other (last picture) as a Tetralia crab, safe and symbiotic, and put it in the tank with the coral. But I'm stuck on the one pictured in the 1st and 3rd pictures. The color matches the coral closely, and the body shape reminds me of a Trapezia which makes me think that it's commensal.
<I agree on both counts>
It's legs are a little bit fuzzy though. One claw is slightly larger and a little bit sharper, the other is smaller and has flat tips, clearly intended for gripping and scraping. I've been Googling for a couple hours now and haven't been able to get a good ID on him. In the meantime he's in a critter keeper with an airstone. So, should I put him with the colony
or would it be wiser to let him test his fate with the mantis?
<As stated, I'd keep all>
Thank you!
-Dan
<And you for sharing. Bob Fenner>