Sand Slug ID? Possible Pest?

[Mechaninano]

I was digging around in my tank's sand today (looking for a possible fish corpse) and I found this slug thing. I was hoping someone could id it and let me know if I should keep it or get rid of it. Thanks in advance.

http://i1093.photobucket.com/albums/i425/brandydupuis/Fish%20Tank%20Stuff%2025G/TankSlug.jpg

[High tide]

Peanut worm, nothing to worry about.

[Mechaninano]

Ok good, I've put it back into my tank.

Thank-you.