Parasite or Harmless?

[Bryceguam]

I just noticed a really long worm last night that lives in my sand bed. At first I thought it was a red thread, but then it moved. It is at least 6 inches long and less than a mm thick. What could it be?

 

[joy13]

Here is a place to start researching Worm Hitch Hikers I find it helps to keep a magnifying glass by the fish tanks just so I can get an up close look at what I am trying to id.