Black Algae?

[Wwidener]

Found this in a clients tank. Black algae? It hasn't killed anything but it also wasn't touching anything. There were two nice size pieces.

Also, do you think that's aiptasia or a duster. She has a nice size aiptasia crew and established tangs. Thanks.

 

[melosu58]

Some kind of sludge. I just siphon it out.

 

[Sniperhank]

That is a feather duster for starters.
As for the black, can it be blown off? All I see is a sponge. It can be nice or a nuisance, depends on your point of view.

 

[coralbandit]

Feather duster and cyanno..
It is not always red .