Can someone id this for me?

[Seansea]

Anybody have any clue what this is? Got it in a couple spots. Appears tonhave a skeleton with a black skin.

Is there anything that eats this stuff?

 

[DaJMasta]

How does it feel to the touch? Honestly it looks like a flatworm to me from the Pic, there are a number of all black with a bright rim, but unless it's moving, it's not that (and it would move on the regular.)

If it's sort of squishy and a little slimy, probably a sponge and the rim isn't that significant, but there's a chance it could be a colony of tunicates too - you would see some small, clear, round openings in a cluster and they would contract slightly if touched.

 

[Seansea]

Not a flat worm. Just growing in place. Does close if you touch it. Might be tunicate. What do you do to eradicate tunicates?

 

[DaJMasta]

They don't harm things and I consider them interesting, but they die on their own most of the time - they're filter feeders so if you don't feed phyto and powdered foods the odds are already against them (and yes, it's common for them to grow for a bit and then die out.)