growing critters

so my tank is finally startin to get stuff growing that i didnt buy!
i found a small tube worm of some kind that looks like a feather duster, only it has a hard tube, anyone know what it is. its only about 1/4 inch wide at the fan spot but its got a bright pink fan. it looks pretty cool. i also have something that looks like a feather dusters head, but it doesnt have any tube. the suck back into the rock really quick just like a peather duster. they are popping up all over the tank, but they are only about 1/8 inch at the feather part. but whats really weird. i have part of a peice f rock that opens up,,,,, in the opening it looks just like a clam mantle. but it doesnt have any shape for a body. its like its part of the rock. never seen anything like it. i got a pic today when it was open, but i got to get them developed and scan and all that stuff. the tank is just growing stuff everywhere, its startin to get really cool!
are isopoods the ones that look like the little peel bugs you find under rocks outside that roll up into a ball. ive got a bunch of those and alot more of the little tiny bugs that are too small to identify. thining about getting a fuge. i really want a mandarin but i know they need an established tank. how much longer should i wait after i get the fuge??? how long will it take the fuge establish a good pod colony???? thanks again peeps!!

dont know how much it holds but it was in intank fuge that was 24 inches long,,,,, 6 inches high,,, and 4 inches deep. im trying to get a 135 tank in may.... so hopefully i can just get a good sump going. maybe use my 55 as the sump/refugium. im not getting any fish untill i get a bigger tank anyway. lost my clown yesterday. i didnt find him till i messed wiht the power head. the bottom had fell off and he got sucked up in it. that sucks because he was the first fish i bought after the tank cycled. that picture looks exactly like the worms/dusters whatever they are that are in my tank. how big will they get? i moved around some of the rock so they would be visible. thanks for the help.

well the plan will be to set up the 135 and let it cycle. then start adding LR to it untill i get at least 150lbs in it. then start transfering stuff untill i get all the fish/rocks/critters out of the 55. i guess it will probably take me about 3 months or so after i get the 135 before i would be ready to put fish in. I have had some problems with the 55 that i think i can correct with the 135. i got another question too. how many ,,,, lets say tang size fish, could i put in a 135. what would go good with a yellow and blue tang? if i cant get anymore tang size fish,,, what smaller fish offers a good color contrast to a yellow and a blue? i would really like to have a mandarin and some firefish gobies. could i put a madarin and lets say 4 firefish gobies in there? does anybody else have tangs that like live brime err.... bryme. my blue tang loves it.