Why do fish bite other fish tails

Question
I hve a sea angle and a gold fish in a tank. The sea angle always bite the gold fish tails? Even the tank is quite big one and enough to swim in...But still. How to overcome it?

Answer
Hi Amal,
 Sorry but I don't know what a sea angle is.  Do you mean an angel fish?

 Fish are often territorial and that is why one fish bites another fish.  

-- Ron
  rcoleman@cichlidresearch.com
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