I only have a few fish (now anyways) a couple of green chromis, a
maroon clown and a 6 line wrasse.

All appear healthy, happy and get along. However from time to time,
one of my fish just dissappear. They are eating fine and look fine,
and then overnight they dissappear.

Today I noticed that the 6 line wrasse has a huge chunk out of him.
How can I find out what is attacking my fish?