Flatworm or Chiton or... ?

[Strad12]

Hoping someone can help me ID this critter. I found it on the glass underneath the sand in my nano cube. It's a little over an inch long, pretty flat, and has some sort of exoskeleton. It balled up like a Rollie-Pollie when I pulled it out of the tank. Should I be concerned about there being more of them in the tank? I don't see any evidence of corals being eaten or otherwise bothered. I'm running a mixed reef with primarily LPS, with a few flower anemones and SPS frags. I would like to add a clam soon, but I'm worried there are more of these and that they will bother a clam.

 

[KJ]

Chiton.

 

[JPM San Diego]

Chiton

How to tell them apart: (text from Wikipedia)
"Chitons have a shell composed of eight separate shell plates or valves. These plates overlap slightly at the front and back edges, and yet articulate well with one another. Because of this, the shell provides protection at the same time as permitting the chiton to flex upward when needed for locomotion over uneven surfaces, and even allows the animal to curl up into a ball when dislodged from rocks. The shell plates are encircled by a skirt known as a girdle."
Flatworms:
"The flatworms, ... are a phylum of relatively simple ... unsegmented, soft-bodied invertebrates. Unlike other bilaterians, they are acoelomates (having no body cavity), and have no specialized circulatory and respiratory organs, which restricts them to having flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion. The digestive cavity has only one opening for both ingestion (intake of nutrients) and egestion (removal of undigested wastes); as a result, the food cannot be processed continuously."

 

[dhanking]

It is a chiton. Pretty cool. It eats algae so it won’t hurt anything.