Some kind of worm

[clownfish26]

I have some kind of worms in my tank are they bad.

 

[hairymushroom]

Most probably bristelworms, no they are not bad. Are they in the sand?

 

[clownfish26]

yes in the sand and sometimes on the glass

 

[bheron]

all worms i know of are beneficial to the system. best if you can get a pic or try to find one here or on the web and post it to be sure!

 

[Sk8r]

THey clean where snails can't. The bristles will sting, so don't touch them, but they're harmless to corals and fish.

 

[Paintbug]

not all worms are beneficial, but most are. take a look at these 2 sites and see if you can ID from there. without a pic or a much better description its impossible to ID any worm.
http://www.melevsreef.com/id/crawls.html
http://www.xtalworld.com/Aquarium/hitchfaq.htm