Some live rock questions

[MeggyPuff25]

Ok so now that my salinity is at 1.024sg im slowly adding live rock, I have abour 6-7 lbs atm, LR is $10/lb here so its slow going for me lol. Anyways I just went to feed my 2 gsp's and I was looking at my live rock and on the one that has alot of coraline algae I saw tube like thingys with little hair like stringys coming out and then going back in, I dont really know what those r so I'm hoping someone here can tell me. Also I noticed these little tiny shrimp like things crawling on the bottom. They were fast so i couldn't get a pick but they are kinda clear with a small strip, it looks like the have pinchers but they moved fast, I was wondering what those were as well. There seems to be a few of them living in the tank atm, not sure on how many exactly though. Thanks in advance and hopefully I will know wht these strange things r that have taken up residence in my tank.

[MeggyPuff25]

On other thing, on the other piece of live rock I have what looks like and feels spongy, it's a yellowish color. Anyone know what that could be and if it's good for my tank?

[MeggyPuff25]

Well I did some searching on the net and I think the little critter that I saw in my tank is a Cirolanid Isopod. Anyone know more about em and how to get rid of them? They must have hitched there way on the last piece of LR I bought. Still dont know wht the other things r.

[Pufferpunk]

99% of all hitchhikers are good, including yellow sponge.

[jdak]

$10/lb OMG.

[Brandon8521]

Thats the average around here aswell or you can pay 7.50 for their uncured liverock.

[jus85411]

crazy! most LFS around me the live rock goes for 4.99-6.99/lb depending on type. usually cured too, never have any smell on them and the main one i go to goes through live rock quickly so it must be a good place to get it.