What are these...

[4n2xtacy]

Hi guys during my daily watch on the corals, I saw these bunch of black egglike stuff under one of the Acans. Question is what are they, should I be worried, friend or foe?

 

[Hemmdog]

Bubble algae, foe. They spread quickly and look bad.

 

[Jensworld]

Take them out carefully and don’t bust them or they can spread quickly.