Shiny black pearl?

[Cliff]

Anyone know what this is?

 

[fastrd400]

Just a guess, but looks like bubble algae.

 

[Aquarian]

Yep bubble algae, get a emerald crab.

 

[ErinCahir]

Bubble algae for sure. You can also CAREFULLY pull it off the rock. Make sure not to pop it.

 

[Cliff]

Thanks folks, I'll try and get it out.