Black Tissue On Branching Hammer?

There's this black tissue or something growing on the branch of my hammer. What is this and is it harmful? If I were to frag this off the branch of my hammer would be very short. I included a pic, it's kind of dark so it hard to see but you can see the branch and then black stuff growing on top of it.

 

Encrusting sponge is what it looks like. Some types of sponge are really invasive fyi.

 

What could I do to get rid of this? Should I try and scrape it all off the branch?

 

So long as it says down on the skeleton it's harmless; that part of the coral is essentially inert.

 

Over the last couple of months it's been growing higher. Any other suggestions? Never seen this before. It's also on my frogspawn branch. For both frags from the same reefer.