Arrow Crabs?

My 120 gallon is somewhat lacking in my invertebrate department. I have plenty of snails and hermit crabs, but little else.



So I was thinking in investing on something that has a bit of size. Arrow Crabs are a bit flashier than most due to their long legs, tall body, etc.



So can anyone gimme some words on these buggers? I heard they may attack other tankmates like shrimp and such. I also hear they are reef-safe though.