Is This Black Sponge?

First off, is this black sponge? I assume so, though it looks more like candle wax than the sponge I see sold...

Second, is it ok to have in my tank? It's kind of everywhere, in between rock, on rock, etc.

I have noticed that as one in particular piece has grown, my xenia coral has shrunk to almost nothing.

Here's one example, you can see the xenia kind of looking blah.

 

hmm kinda interesting... May i ask where you recieved the rock from..? Out in the wild or at your lfs...

Here's a link of indo pacific sponges i didn't see a likely match, but you can dig around there..

Link: http://www.marinelifephotography.com/marine/sponges/sponges.htm


Best of luck..

 

Looks more like a 'fire coral' to me, which is more closely related to a jellyfish or anenome than a sponge or sps.

Be careful though -- if it is that, they can hurt a lot. Might explain your xenia condition.

It is beautiful though!

 

I got the from from a local shop.
I asked the owner today, and he said he sees it pretty frequently. You can just break it off if you want he said.

It actually breaks off on it's own, there's little pieces laying around on the sand as well.

As far as I can tell it's just a hard piece of candle waxy substance, it doesn't move or anything, and the same guy said it wasn't harmful unless it grows over a coral or something like that.

I'm not sure... it doesn't really look like black sponge photos I see online, but it's black and unknown so I assumed it was.