strange critters

[ABATTLEDONKEY]

hello,
in the course of scanning the RC forums, ive noticed that alot of strange critters and bugs happen to apear in SW tanks from possibly out of no where. ive had a 30 gal SW tank now for about 3 months. i've never had a critter, and never had any unusual.....anything. the only thing ive ever had was the fish i put in the tank, the sand and the rock. well i upgraded my tank today and made it a 55g. i purchased dry sand since my bio load isn't going to go any where and am not purchasing the rock till tomorrow, well when i moved the LR into my new tank, i noticed that i finally had a strange critter. 2 in fact. one was a long centipede looking creature and was bright pink and purple . the other looked more like a plant. it was very soft, almost fuzzy, was cone shaped and had a hole at the top. aside from the blatant femininity these creatures brought to my tank, im curious to know if they can cause any harm. should i remove them? are they a good sign? sorry, but i dont have any pictures as they were small and the only camera i own is on my phone. any help with this is very appreciated. or mabey is there a goos web site i could go to to learn more about anything that might come up? thanks
-Paul

[FBNitro]

Check out this site for a list of hitchhikers:

http://www.xtalworld.com/Aquarium/hitchfaq.htm

or

http://www.melevsreef.com/id/

[Jake_07]

the long centipede looking creature is probibly a bristle worm they are good scavengers

[Paul B]

At one time or another I have had, with the exception of maybe two or three, all of those animals in my tank.
Those shelled black slugs were the nicest and they have appeared a few times and get about 2"