Is this a pest?

[Navyblue]

http://i3.photobucket.com/albums/y85/Navyblue/Aquarium/Others/img_1959.jpg

[graveyardworm]

In some peoples tanks, yes. Best to remove it while there isnt much. Be careful not to break vessels. Turn off circulation and use a siphon tube right at them while you try to remove them just in case one pops. Mature vessels contain spores and if it pops they could be released into the water column and cause it to spread.

[Navyblue]

Hmmm... I think I saw a few that is broken off... Thanks..