All I can think of are Planarians or Nematodes. If you bother them, do they get shorter and fatter, or do they just stay the same shape? Any way you can get pictures? If it is either one of those, they are pretty much harmless, you just may be overfeeding, or not removing decaying matter quickly enough.
Come to think of it, you said they were floating all around -- if you mean kind of swimming, then it's probably nematodes.
Either way, 100% water change, gravel scrub, and trim dead leaves from any plants. No food: No worms.
Last edited by TakingthePlunge; 07-08-2013 at 08:53 PM.
Reason: Sudden realization