What is growing on my rocks?

[Dustinba]

As the title says, need help identify what is on my rocks. I recently started a new job, and my cleaning schedule slipped for the past month. After giving the tank a good cleaning today, I noticed this. Any help is appreciated

 

[Dustinba]

Not sure if the movies will work, but that’s the best way to see it

 

[Dustinba]

Top of the photo, I noticed this as well. Looks to be clear tentacle looking things with debris all on them. Moves with water current

 

[KJ]

Sponge.

 

[Dustinba]

Sponge.

Sponge being the white thing? Assuming sponges are “harmless”

 

[reef lover]

Yup sponge. Harmless. And i dont see anything in the first pic.

 

[Dustinba]

Yup sponge. Harmless. And i dont see anything in the first pic.

Yeah it’s hard to see in a stand along photo unfortunately.

 

[reef lover]

Might be able to get a better pic with the blues off and whites on. I might see the tentacles of aptasia there...