Id please!

[irene060606]

I have recently seen small tubes erecting from the substrate in my tank with tiny opaque worms waving out of them. I can only seem to be able to see them @ night with a LED flashlight. There are dozens of them lacing the bottom of my tank. I would appreciate it if someone could tell me what they are and if they might be doing more harm then good. They range to about an inch in length. Thanks