What are these??

[bumperbeetle]

Hi All!
Ive had this tank up about 10 months now. I noticed a strange large black slug looking this grazing on one of my LR's last night...never seen it before! Today Im noticing all these..egg sacks or pods all over my rock and I want to make sure it/they arent harmful! Ive had a shrimp and coral beauty die suddenly over the past few weeks so Im a bit nervous I've got something lurking in there!

What are these?!?

 

[kschweer]

Valonia, better known as bubble algae. It's not harmful to fish or corals, but can grow quickly and become a big nuisance. Mr saltwater tank has a good video on getting rid of it.

 

[WindeyD]

Bubble algae for sure; it is a nuisance algae and I would advise taking steps to get rid of it.

 

[Shep]

Agreed, those are bubble algae. Not sure about the slug, could be a nudi of some sort. AS for the deaths, test your water ASAP and let us know the results.

 

[maroun.c]

Bubble Algae,
I peel those of the rocks without letting them explode and get rid of them. They tend to go out of control if left unchecked.

 

[rajkovich207]

He says slug in the op though. Just for giggles I'm going to throw a guess at it. Look up stomatella snails if you don't get a more suitable answer.