Help ID - what is this slug?

[otter]

Just saw this ugly critter last night and am not sure what it is? Intentional cleaner or is the is a nasty hitchhiker?

It sort of looks like the rock in these pics but when you zoom in you can see its maybe a tan or neutral color??
Sorry if the pics are bad...

 

[cloak]

Stomatella snail. :thumbsup:

 

[otter]

Many thanks!
Perhaps I should hope he/she/it multiplies

 

[Newstead]

+1above. They are great to have in a tank - algae eaters. Every once in a while I see the puffs of "smoke" from their spawning. Even got it on video a couple of weeks ago.

 

[primetyme941]

Same here. I have a whole army of them now. Mine have red shells which I think add some color as well.