Branching hammer coral black mat on branches?


Premium Member

I got this frag about 2.5 weeks ago, and it has always had a couple of patches total of 4 of what seems like a black mat, all of them smaller than half a square inch, the biggest one I took a picture with the lights off for clarity (so the heads are fully retracted), it seems some sort of bacterial mat?, I also found on google something about a black band disease which is the only match I got for a search on this, but that definitely doesn't seem like what this is. It can be scratched off, and I think it is harmless?, I have the hammer coral on my 10g QT tank along with another branching hammer that does not have any signs of this black mat. The black mat is the same size it was when I bought the frag. I will likely be moving this 2 hammer corals to my DT tank in 1 or 2 more weeks and I want to make sure I don't introduce anything I don't want. Both hammer corals have been fully extended since day 1 in QT, and the heads themselves have no black anything or any sign of disease.

Any ideas on what this is (in red square)?, should I try to scratch it as best as I can?.

@Mike R wrote:
Is it soft and "snotty" in texture? said:
It is a little soft, but not too much, it is rather slim, I would not say it is snotty in texture, more like a plaque, near the center it does bulge up a little. In all the other spots except for this one, it is around the base of those mini heads?, the ones that kinda look like vermetid snails, but are actually mini heads (although some of them were vermetids I removed), my other hammer has many of these, and they actually have mini polyps!.
I've never seen anything like that before, but if it were mine, I think I'd try and remove it. You think it'll come off with a toothbrush or would you need to use a scalpel or similar tool to scrape it off?
I haven't really tried to remove it, because I though it might be part of the coral, I do remember accidentadly scratching it with tweezers while removing a vermetid snail, I doubt it will come off with just a tooth brush, but anything rigid will do it. I will probably remove it this weekend during water change and use the water to rinse and remove.

I looked up black sponges and that does look like it quite a bit, mine does not seem to have any pores or tubes that I can see though.