need identity help. Little bugs?

[mach]

Hey guys, I need some help identifying these things. They only come out at night after the lights go out. There are dozens of them in my tank. I have only observed them on the live rock. Not on any corals. They dont move too fast cause ive never witness them in motion. All I know is that they are no where to be found when the lights are on. They have a hard shell, and have distinct black spots on them which you can see in the pic. They are real small about the size of rice. I recently lost my powder blue tang. He got real thin, real fast. Within a couple of days he was dead. My worst fear is that these bugs are parasites which caused my powder blue's death.

Any help is appreciated.
Thanks
Anthony

 

[Dubbin1]

Look like chitons.

 

[divewsharks]

i second that...

 

[Paintbug]

yep chitons it is. 100% safe and great grazers! look here under snails. http://www.melevsreef.com/id/kritter2.html

 

[mach]

thanks for the help people. I was really worried about these things. I was ready to take a drastic course of action. Lucky for me they are beneficial