Found a stowaway

[SLCarrillo]

Found this guy, haven't added anything new to the tank in over a month and he just appeared. Seems to be cleaning and minding his own business. He looks like a snail with no shell. (I think we call those slugs? Lol )
I am not putting corals or anything in here so is he safe to stay or should I pull him out?

 

[Lionfish Lair]

It's probably a stomatella.

 

[SLCarrillo]

Thank you :D