Slimy spot on rock.

[Hitachi]

I found a spot on a rock today that is slimy and under better lighting looks purple. Can anyone I’d it?

 

[fishguy242]

hi,hard to tell,looks like black sponge

 

[Hitachi]

I hope so, that would be cool.
Thank you.

 

[SHNICI]

I hope so, that would be cool.
Thank you.

Have on mind most of them are invasive (the black sponges) too are destructive to the LR and the creatures inside. Also if something disturb it on place (fish, invertebrate) it can nuke the tank with poison, after all can start smell like rotten eggs.