Hitchhiker crab ID?

[Kyuubi]

Found this little guy chilling on one of my live rocks, he was small enough to get siphoned up. Can anyone ID him so I know if it safe to keep him with my corals? Thank you!

 

[Rtaylor]

Gall crab?

 

[Kyuubi]

Gall crab?

Bad or good? Should I put in in my mantis tank?

 

[Reefer Reboot]

@Rtaylor is right, Gall Crab. Get rid of it.

 

[Cell]

Lots of gall crab posts lately.

 

[Kyuubi]

@Rtaylor is right, Gall Crab. Get rid of it.

It went into the mantis tank for food lol