saltwater centipeed?

[kellehar]

sorry i have so many questions but i never saw any of this stuff in my freshwater tank. Tonight as i was looking in my s/w tank at my live rock i saw what looked like a very small white centipeed. any idea of what it is? is it harm full to fish or any other marine life? I only saw it for about 20 seconds as it went back in to the live rock.

any ideas would be helpful
thanks
justin