Here is the official info on my little friend.Your chiton photo was interesting and immediately my wife stated that it was a Cryptoplax larvaeformis. I knew she was probably correct as she was the chiton expert when we worked with chitons starting way back in 1963. I looked up the chiton in our literature and the photos say yes along with other things. It officially is Cryptoplax larvaeformis (de Blainville MS, Burrow, 1815). What that all means is that a man named De Blainville had a manuscript describing this chiton in an 1815 publication by Burrow. I imagine you probably do not care but that is the official information. It is a common species found in the Western Indo-Pacific region which is where most of our "living rock" material comes from.
Now the modern info. We probably get more questions on this chiton than any other from marine aquarium hobbyists. I imagine that there are a couple of reasons. First it is quite secretive so it gets collected with the "living rocks" and sold for your aquarium. It also must be a hardy species as it takes the transfer nicely and third it seems to adapt well and lives well in the home aquarium.
If you would like to see some beautiful photos of this chiton, which grows to about 4-5 inches as adult size, just click this link and I hope you get to Poppe's page for C. larvaeformis.
http://www.poppe-images.com/images/s...tegory=chitons. If this does not work you can copy the website address or give Goggle a search for the Genus and species and then pick the Poppe listing.
You say that you have had the chiton 2 years. Have you seen it eat? It is a radula feeder and that is best explained by saying it scrapes a "blade" called a radula on smooth surfaces for food.