need to identify this critter!

[attilak]

This is the strangest critter I have seen ... first time I seen in my tank and I would say its about 2", very flat - I would say no more the 2mm thickness. See pics, took a pic from both sides.

 

[vetteguy53081]

Chiton and a reef safe algae eater

 

[attilak]

Thank you! funny, I have not added anything to my tank in months so it must have been living in tank for a while as long as it's nothing I need to worry about. I wonder how large these get in captivity as I did some research and they seem huge when I look at some pics.