Weird thing in green slimer

[qhduong]

Anyone know what this is? Found it on my green slimer today. Yesterday I saw my hermit crab at this exact spot eating something.

 

[Impala67]

Looks like discoloration of the coral. Could be a self defense mechanism against the hermit crab I’ve had one do that before. On a side note what type of hermit crab?

 

[qhduong]

Looks like discoloration of the coral. Could be a self defense mechanism against the hermit crab I’ve had one do that before. On a side note what type of hermit crab?

I think blue leg hermit. He's pretty big...

 

[Impala67]

What might have happened is the crab might have taken a couple chunks out of it mistaken it for algae. I’ve seen this before just keep an eye on it if it gets worse lower your lighting a little.