Hello everyone,help please

I have seen some of the threads from your group and had no replies else where so i thought i would try a local forum for some help.
I haven't had a marine aquarium very long and there are some things that are a little confusing.
There is this taping or loud clicking sound coming from my tank.
Like little hard stones tapping against each other,do i have asomething wrong with my tank?
I have turned of the power and it continues mainly late before bed?

It would be a Pistol Shrimp. Everyone that has a tank started with live rock from an LFS will most likely have at least one in their tank.

Their not really anything to worry about. If you leave the lights off at night, get a torch and either a red bulb or put some red celophane wrapping i think its called over the end of it, and look at the tank with the red light you might see it somewhere, or if you turn the lights on and look around really quickly before everything goes back into hiding.

If its a mantis on the other hand, that'd suck.

Found it
It is one of those pistal shrimps with the one big nipper.
What is so bad about a mantis shrimp?