I should imagine it's planaria. They are harmless and usually occur as a
result of over feeding. Try reducing your feeding slightly and doing a good
gravel vac and hopefully you'll suck em all up!
Mel.

"Geezer From The Freezer" wrote in message
...
I notice a little worm, probably no less than
5mm and no bigger than 8mm, and quite thin in the
tank, at first I thought it was plant debris
from the stems or the root, but then I noticed it
wriggle. It is white in colour. What is this and
should I be concerned?