Live rock with black area??

[sdivell]

I noticed tonight that I have a piece of live rock with a black area on it.  the back comes off on my finger if i touch it. 

Is this rotting?  should I pull it out of my tank?  I've got it in a section of my sump by itself right now.



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[Vincenzo.]

from what i understand, it's from excess nutrients in your tank. another reason is natural light shining onto your tank. or could be a type of cyano. or could be a sponge.

[JD]

I don't know what it is. If it were mine I would pull the rock scrub it off in old tank water, rinse the crap out of it then put it back in the tank with that side exposed to the lights, presuming that side was down. Anything black like that makes me shiver...

[Hookup]

probably just a sponge

[JD]

I though a sponge covering that large of an area would be difficult to remove?

probably just a sponge

[Hookup]

I though a sponge covering that large of an area would be difficult to remove?

I've had some "stuff" that I'm calling sponge that has that kind of consistency.. but it could be anything... in fact, i'm looking at some of it right now in my tank.  Last time Pat was over, he also thought it was a sponge...  but i do not think anyone's willing to put money on the id.. :0

[Tyler.L]

i have some too i dont know what it is but i honestly think its just the rock thats got a black spot on it....leave it

[az]

black sponge, probably dead by now.