Here is the thing based on what I learned from an invert specialist -
Most crabs are predators, and most crabs will eat the things that we want to keep in our tanks.
That said, a few are not and are okay to have - until they develop a taste for those things we want to keep in our tanks because they have never been told that they are not supposed to want to eat these things....
However, catching them can be a bit tricky. If you want to keep everything in your tank just so, best bet is to remove him. On the other hand, he is very cool-looking, may be hard to catch, and may not do that much damage - is it worth it to keep him and consider him one of your pets as well? That is your call.
Good chance he'll eat (or at least pick at it ) something you love at some point, if not sooner, then later.
The food in a bottle trick works for many. I've been advised more than once that skewering them with a sharp knitting needle, for example (ala spear-fishing) could work. I have never tried it myself.
also, just so you know, these animals are EXTREMELY difficult to identify. Suffice to say, it belongs to a group of mostly predators.
Good luck!
