White algae id?

[willforr]

There’s this slimy white film under some of my rocks, not sure what it is. I’ve noticed it growing for a while so I’m wanting to know if it’s something to be concerned about. I don’t think it’s photosynthetic because I only see it under the rocks away from light.

 

[fish farmer]

It might be sponge.

 

[vetteguy53081]

Poriferan sponge, likely cryptic sponge Pull off with dental pick or small crochet needle before it becomes evasive to the coral