Crab with little bugs on him?
 

I have a pink emerald crab who is a nice guy in my reef tank. For the past few weeks my reef tank has been sans fish - they are in the hospital tank. SO, the reef tank has had quite the copepod explosion, and some other type of explosion. I have noticed that on the carapace of the crab there are very tiny little bugs crawling all over him. Very tiny, there is no way I'd be able to get a picture. I don't think they are baby copepods, they travel rather fast. I see the baby copepods on the glass and they just sit around for the most part... I am not sure if the lice like thingies are bugging the crab or not. Any ideas what this is?

I know exactly what you're referring to. My green emerald had these and they are so fast. They remind me of electrons orbiting nucleus.

When the crab would shed I noticed the bugs were gone for a while then would slowly return. They didn't seem to be harmful. Mine were orange.

They are fast... creepy fast! The crab does look dull so I bet its the exact same thing then, he looks ready to molt. Well, I am glad they are not dangerous to him.

Thanks for the info!!