Pest or not?

[Ohhithere]

Recently found this "thing" cruising around on my sand. I'm not sure if this is a cool hitchhiker or if it's bad. If anybody knows what it is, I'm open to suggestions. Bad picture, but in the pic it's half ok the glass, I will post another in the future. Thanks!


Current tank info- IM Nuvo 30L

 

[AlSimmons]

It looks like some type of sea slug. In most cases these are bad so you might want to remove it just to be safe.

http://www.advancedaquarist.com/2004/10/inverts

http://www.advancedaquarist.com/2004/12/inverts

 

[Ohhithere]

Better Pic