Something eating my leather coral

[fishkeeper8774]

My leather coral has been doing healthy until recently when it started losing its color and rotting. I check again and I find a small hole in the base that goes pretty deep. What kind of critters is that???

 

[fishkeeper8774]

Idk if this helps but the hole is abt half a centimeter in diameter

 

[KJ]

Coral Gall crab.