Slug/Snail ID

[Reigun]

Anyone know what this is? Looks like there’s a hard shell under the skin. After removing it, the shell appeared like defense mechanism.

Moved it to the sump for now. Not sure if this is a good or bad critter.

 

[dbraun15]

Pretty sure it's a Deer Cowrie...if so, good algae grazer, but can get large and knock frags/small rock work.

 

[Reigun]

Thanks! Cool looking snail and they nice pretty fast.