Verified answer

No, spider crabs like to rip up corals and put them on their back, which unintentionally kills the corals and their colonies. They aren't considered reef safe, but if you have a Fish Only With Live Rock, and you can buy a zoa colony, or some kind of soft coral that you can spare, then you could keep one.

Decorator Crab Reef Safe

according to freshmarine.com spider crabs are semi- aggressive, but others comment that they are peaceful and not reef compatible, plus they're omnivores, you could try it but it may be the end of part of your reef.