weird clear slime on live rock?

[Sinister]

hi guys i met someone that is shutting down there tank and i got my hands on a bunch of live rock but it has a weird slime growing on it is this bad

[Sinister]

Update is this a bristle worm or a pest it was on the rock too

[TheKid]

Pic 3 is bristle worm

[bvlester]

first 2 pic's are of spunge forming I believe and the 3rd pic is of a bristle worm good thing.

Bill