I was wondering how to tell if a slug is good or bad. I have removed two slugs from my tank and found another one that i cant get to yet.... how can i identify them? Where the F*** do they come from? and should i bother to worry? Thanks for the help.

are you sure they are slugs, and not something like bristle worms or something along those lines...

A pic would help.

I bet you anything there Stomatella snails and those are good look at a pic of these first before you take any more out

You might want to take a glance at the Ultimate Identification Thread before you go on a killing spree. Always pays to be 100% sure about the creature(s) before you terminate 'em.