What is this???

I'm kind of a novice with my reef tank that we've had for a year and a half.
For the past couple of months, I've caught a quick peek at some critter that
I had never seen before. I didn't buy him, and like I said, had not seen
him for the 1st year. He only comes out at night (I assume). Well, tonight
I snapped a couple of pictures. They are not great pics, but maybe good
enough to identify him. He is about 2" long (maybe a tad more). The link
below is to the picture. I would appreciate any info.

Thanks!
Wes


http://img401.imageshack.us/img401/4669/whatisitfo9.jpg