It looks cool, can I keep it?

From across the room I saw something floating around in the middle of the tank, my Chromis and my Goby both gave it a shot to eat, but they all decided it was best to leave it alone. After swirling around a little bit it found a home in the middle of no where, somewhere between Lincoln, NE and Denver, CO. I've gone through a lot of older threads looking for anything similar to what I have, but only thread I found that was close, no one answered. I'm hoping I get a little better luck. Sorry for the crappy pic's I'll try and get better ones tomorrow If I find him again. Or find a different one.
So I'm wondering what this is and can I keep him? heh

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