Worms!
 

I just got my new tank set up. I was watching the tank one night and I saw a shirmp of some kind. So im using a bottle trap with some shrimp in it to try and catch it. While obseriving it i notice TONS of worms trying to get at my bait. They are as long as 30 sm streched out. They are brown and kinda flat with many spines along the sides. They live in the live rock and only come out at night. what are they and are they harmful to my tank?

30 sm is that long

Do thee worm things look a lot like centipedes? They're most likely bristleworms. They are, for th most part, harmless and just eat detritus that falls to teh bottom of the tank. If your set up is a reef however, you might want to consider taking out the big ones (like your foot long bad boys... these guys can get much bigger if you let em)

Oh btw, don't touch em barehanded if at all possible. They can sting you.

anything over an inch is bad.they eat shrooms

I have mushrooms and I have lots of bristleworms larger than an inch (and other types of worms as well) and I haven't seen a 'shroom disappear as yet.

Actually, the bristle worms haven't been detrimental at all in the aquarium, just the opposite - detritus and decaying material eaters.

I have all kinds of worms in my tanks and they are good thing to have, they clean up a lot of Cr*p from your tank.
People dont like them because they look ugly but, worms may think the same about humans, we never know?
The only bad one is medusa worm http://www.seahorse-nw.com/Predators/IMAG031.JPG
(do google picture search if this link didn't work)
If this one dies all your fish will go to the fish heaven , same as black cucumber.

medusa worm? never heard of it. is it toxic?

It is when its dead.

ya most are beneficial but be cautious.check out oregon reef.comhttp://www.oregonreef.com/sub_worm.htm

Ok, but that's a prize-winning worm he has there :lol:

ya probably not common

yah im thinking they are bristle works, they look like centipedes. There are lots of them tho ranging from one 2 cm to about 30 cm. How would I go about taking out the big ones? They are so fast and live right inside the live rock. As long as they are not harming much I can live with them, although they are really ugly

As a family of worms, the Eunicid (Oregon) are pretty common. Different species acheive different maximum sizes though. I've kept a number of them in my tank for years. At one point, there was one living in the sand bed that was over 2 feet long. (He stretched nearly 3/4 away around the circumference of the tank)

I've observed the largest to eat mostly macroalgae. The smaller ones seemed to be scavengers of whatever they can grab. I long suspected that they are the reason that I can't keep Xenia in my tank, but have never actually caught one in the act.

As for bristleworms, it is pretty easy to separate the good from the problematic. There are some that will eat coral, but in order to do so they need to latch onto the coral and scrape at it for hours. As such, it is pretty easy to catch them in the act and remove them with tweezers. If you just see the worm in/on the sand, I would leave it be - even if it seems large. (unless you just don't like seeing them at all, but that is an entirely different concern)