PLease help ID

[Learningone]

I am new to salt water tanks and I have just finished cycling it. I introduced 2 Scarlet Hermit Crabs, two Green Emerald Crabs and two turbo snails to start with two days ago. I noticed one of the Emerald crabs has two white circles on it. I did not notice if he had them when I put him in. Is it something I should be concerned about. I have nothing else but rock in the tank right now.

 

[ThRoewer]

Those may be just some hard tube feather duster worms.
I have thousands of those growing in my tank, preferably in shaded or dark areas with a good amount of flow.

 

[jraker]

Spirobid worms

 

[Learningone]

Thanks for the information. I was worried I already had a parasite issue.

 

[snorvich]

Thanks for the information. I was worried I already had a parasite issue.

Ich will only use fish as a host.