im just curious what your alk, cal and mag levels are? you never posted anything about them. also what kind of lights are you running?
the tangs should really be in a larger tank. IMO a single tang shouldnt be in a tank smaller then a 75. do you plan on upgrading soon?
the CB shrimp may or may not rip the arrow crab to pieces. these guys seem to be a hit or miss with their atitude.
i suggest strongly doing alot of research before making any purchases ESP. BEFORE removing anything from the wild. reefs are struggling as they are and removing things isnt helping. infact alot of places have laws against doing so. there are also proper collection techniques and usually limits.