Red Devil head problem

Question
QUESTION: Hi David---my red devil is about 2 yrs old and 7" long.  In the past few days its head looked unusally red.  It's not eating and looks very tired.  Do you think it's having a head injury or infection?  What should I do?  Please help.  Thanks.

ANSWER: What are the water chemistry values????  When did you last do a water change?  What other events may have led to a head injury??? What is the water temperature in your tank?  dave

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QUESTION: Dave---I do water change once a week.  The nitrite and PH levels seem fine.  I fed the fish some frozen shrimps recently (new diet).  It also likes to jump up to hit the tank cover board once a while.  That's why I suspect a head injury.  The head is really red.  I don't know if anything is related to infection.

Answer
Hi Larry:  There are a couple of reasons why fish change color... Fear of something or aggression and spawning are the two biggest reasons.  The third would be diet and shrimp have a tendency to help bring out the red in fish. So... with your fish I suspect it may either be the shrimp... or his/her desire to attract a mate.   Also with Red Devils... when they are kept alone they tend to brighten up a bit and the males will develop a large lump on their head its called a KOK.  If it is a female then I would look closely at her and see if she seems to be plumping up as though she is carrying roe...  You can offer a different kind of food such as pellets and see if he/she will eat.  If it eats then it may not like the shrimp or the shrimp may upset it's stomach.  If by tomorrow it is still not eating then I would administer a dose of antibiotic such as general cure or triple sulfate.  Keep me posted... dave