Live rock hitchhikers
 

http://www.ummfish.com/tank_hitchers_01_12-8-09.jpg

The tree-looking thing, maybe some sort of colonial worm?

But there's also this crustacean(?), it looks like it's filter feeding off the pinnate antennae. (What a pose.) And there's an amphipod above it.

http://www.ummfish.com/tank_hitchers_02_12-8-09.jpg

I hope you enjoy!

There are some amazing and bizzare things out there. How big would you say it is?

Well, that's sand that it's building with, so pretty small. But it's still big enough to see pretty easily. An inch or so, probably.

i think the first thing is a spaghetti worm...they eat detritus..I have no idea what the brown shrimp looking thing is

I would think spaghetti worm, but aren't they sand sifters? Do they build permanent structures up into the water column?

And we have an answer:

From Ron Shimek: http://forum.marinedepot.com/Topic10....aspx?Update=1

this is awsome!

this is one of my favorite things about reef systems and why i can just sit and stare at the display forever. You never know what you may see. ;)

Gosh that is totally wild

Got a different ID on the funky sand-skeleton thing. Leslie (the worm wrangler) thinks its from a genus (Lanice) of sand-skeleton building worms.

Some information on those:

Here's a scientist's experimental tank with them:

http://www.marinespecies.org/aphia.p...mage&pic=12186

and a picture of the worm, removed from the tube:

http://upload.wikimedia.org/wikipedi...conchilega.jpg

And Leslie's comments are here: http://forum.marinedepot.com/Topic10....aspx#bm105094

Let me start by saying RC is awesome! I've been trying to identify that worm for the last month or so with no pictures. I have the same Lanice Conchilega worm in my tank. I thought it was a piece of something from my arm but when it started moving I couldn't believe it. Thanks for the ID!