Acro help

[iplayhockey1919]

I recently added this guy to my tank about 6 weeks ago. Looking at the pictures from then until now. I noticed a black thing spreading from the bottom. I talked with a buddy mine and told me to scrape it off. That worked a little but it didn't take care of it. Another friend told me that it is rot and I may have to cut new branches off from the good tissue. The question is what is this, what can it do to the coral and how do I get rid of it?

 

[29bonsaireef]

Looks like STN that has algae growing over it. Kinda hard to tell out of the water. If it doesn't get any worse I wouldn't worry about it. All growth in Birdsnest comes from the branches. They very rarely will encrust anything at all.

 

[kevin_e]

That's a Seriatopra, not an Acropora.

Black?Is it sponge-like?

With my bridsnest, old branches temded to shade and turn dark/black with no tissue.

 

[iplayhockey1919]

That's a Seriatopra, not an Acropora.

Black?Is it sponge-like?

With my bridsnest, old branches temded to shade and turn dark/black with no tissue.

It didn't seem like a sponge-like material. The picture above is after it was scraped with a knife, so I am thinking it could just be from an old branch like you mentioned. I find it funny how easy corals are to being misidentified, but super glad it is a birdsnest.