Is this black sponge?

[Arsenix2001]

My 75 has been up and running for a year, transferred from a 38. Battling some diatoms and bubble algea but just noticed this interesting fella on a zoa colony. Is this black sea sponge or something else. Seems to be two spots of it and it is spreading slowly. Good bad? Remove? Pic doesn't do it justice but it is almost jet black in color. And spongy when poked.

 

[blaxsun]

If it's spreading, yeah - I's probably remove it so the zoas can recolonize.

 

[Timfish]

Looks like chicken liver sponge, Chondrilla nucula. It is pretty common and coloration will vary depending on how much light it gets and can be almost white. I've never had problems with it but if it looks like it's crowding your zoas it can be removed fairly easy.