coi fish

Question
Hi I have coi fish in a large tank and I;ve noticed a couple have a bulging eye that seems to be getting larger. could you tell me what the problem is and how I could cure it I love my fish and they are extremely well taken care so I;m puzzled. hope to hear from you soon

Answer
Hi Shirley,
 I have no experience with koi but bulging eyes are often the result of stress.  This could be due to deteriorating water conditions.  Are you doing regular weekly water changes?   You should be changing 25% of the water once a week, every week, to keep your fish happy and healthy.

 Other possible sources of stress are aggressive tankmates.  Could that be a possibility?

-- Ron
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>