What is eating my Live Rock?

[jeffaquarius]

One of my live rock is being consumed by something. The rock is like a cheese with bored holes and one side has been obliterated. Tank is about 1 year old. I used flashlight after dark but could not find anything. Any guess?

 

[Mebbid]

Could it be a rock borer urchin? I thought there was nothing behind the name of it when I bought it then suddenly one day a corner of a piece of my live rock disappeared

 

[jeffaquarius]

Yes that is exactly what is happening when my anemone in front of the rock shivered and I was surprised that behind it the rock is like limping already. I haven't seen any urchin though.