they are reef safe, awsom i think I found my new addition to the tank amazing photos dident even notice the glass was dirty
They are slightly more reef safe than an anemone, as pom pom crabs carry anemones and could sting corals with said anemones.
They are also very small, and only come out at night, so if you have a tank larger than 40 gls, I would suggest you skip these interesting little creatures, as you may never see it.