Is it a pest?

[Lucky luc]

I've found these little dude in my vivarium anyone recognize them. Friend or foe?
https://www.dropbox.com/s/4p662uzst0...apest.jpg?dl=0

[privet01]

looks like a slug. I'd think they'd become a pest quickly. But that's just my guess, I don't know anything about them except they ruin some of the vegetables in my garden.