Pics on alt.binaries.aquaria under the same title.

I found this in some live sand rubble. Is it coral? If so, what kind and
how do I take care of it? It's not soft. It's hard like stone. I have
also noticed on some days the color fades and then gets darker. It was in a
10gal that I haven't had the time to break down. When I looked at it today,
it looked like it had gotten bigger than the last time I saw it. It has
very small tubes protruding from it deep down inside it. I hadn't noticed
them before. Any ideas??

TIA

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D.S.