So my wife came home late from work and she wanted to see the feather duster I found growing in my tank so I turned the light on and to my surprise I found this strange white, almost triangular shaped critter on one of my live rocks. It scurried away really quickly so I didn't get a real good look at it, but it had about 8 or more legs and wasn't real long 1-1.5 cm. It was white. I looked at a number of identification websites and couldn't find anything that looked like it. Any ideas?