Hippo Tang always hiding/timid
In my tank I had 1 yellow tang 1 hippo tang 1 two year old Emperor Angel which is still pretty small but has grown a bit, two purple damsels and one black and white damsel - had the tank for 3 years - 75 gallon and never had a fish die. All the fish got along GREAT and were very peaceful, always swam together as if they were all part of the same school.
Then my yellow tang disappeared - dont know what happened - figured it got sick and died - maybe it was old. I did notice its fins for a while looked as if it had a few missing pieces in it as if maybe some of my other fish nipped at it when it had its back turned.
Anyways after it died I noticed my Hippo Tang always hiding in its normal sleeping spot, not participating as much in the feeding frenzy every time i put food in, and does not swim around as actively as much anymore. First time i noticed it I thought it was sick, or terrorized by the Emperor Angel and would eventually starve to death. To my suprise it still eats, and is still alive. Its been doing this for a few weeks now.
I am beginning to think that without the Yellow Tang around that the Hippo Tang now feels threatened/very defensive. Is this the case? Should I buy another Yellow Tang to put back in the tank to restore some order and get things back to how they used to be?