Black sponge at trachy base, is it a Good or bad one?

[Broberg]

Hello
Can anyone tell me if this is a good or a bad sponge? The Black one. It is at the base of my trachy, so dont Think i Can move the coral away from the sponge and it is my favorite coral

 

[Subsea]

How do you know that it is a sponge?

@Broberg
If I was to guess, I would guess black Cynobacteria. Have you tried gravel vac?