If you are going to keep one they need a fair amount of food or they will become destructive (experience.) I am getting rid of mine soon because while it is behaved and does not go after the large corals and fish it is starting to develop a taste for the bristle worms and pods. Not my first choice of livestock, but they look interesting and do not seem to hide as much as my peppermint shrimp.
I have 2 in my 180 gallon reef. They are both very peaceful and great scavengers. They will feed on any excess food that settles to the bottom of the tank. On occassion they will try to look tough when a fish gets too close, but they are all bark and no bite in my own opinion. They are one of my favorite specimens in my tank.
I had a bad experience with them. Went along for months with no problems then I noticed the clam was not opening like it used to. At night the CBS would climb all over it and pick at it. I think in an SPS tank they'd be OK but they dont have those claws for nothing.
This is a very debatable topic. I think the general consensus is about 50/50. I have one in my 65 gallon and really enjoy it. They are beautiful! But I think I may have a peaceful specimen, because i've heard stories about mean ones that ate other shrimp and xenia. They definitely need a place to be, preferrably a cave-like space that offers him some privacy. They are active at night. Great janitors of any excess food also. I have had mine for a little over two years now.
I have not had any problems with it attacking fish or snails that I know of but they will eat pods, worms etc. I don't want that so I removed it this morning.
I would hardly ever see it anyway so it's no biggy.
i have one in each of my tanks, and aside from the death of my poor neon goby, theyve been fine... i throw in a piece of frozen shrimp once in a while for them to munch on, and they seem to do alright.
one of them is a lot more timid than the other, as he's in a tank with my porcupine puffer. if the CBS gets out of line, puff-daddy usually bites off one of his claws. they stay in line without those
so, coral safe? yes. fish safe? make sure your fish are bigger than they are!