Is this normal or hurting it

my new crab here has been doing this to alot of my corals its kinda worring me but they all come back to normal the next day

 

dont mind the outbreak ofn the back wall my CUC has been kicking butt on it and i have some serious cleaning to do

 

What kind of hermit is that?

 

I ended up getting rid of a rather large hermit like yours. He was quite the character but he annoyed the coral so much I couldn't enjoy them.

 

i have two or 3 of them they dont seem to hurt anything my new CUC has done an awsome job thought my tank was done for and in less than a week they had all the cyano cleaned up

 

Do you have the specific name for the hermit ? People would probably like to know since finding cyno eaters is always a good thing.