pet fish problem

Question
we  pet a Black shark since a 2 months but just from two days we observed that one of them developed colour change that means it lost it`s colour upto some extent weather it is a deases or anything else please replay me as early as possible.  with  Thanks

Answer
Hello Rakesh:  Fish lose color and change color for a variety of reasons.  With Sharks I would observe them for signs of aggression. Aggression in fish tanks is a large concern because it brings stress to the fish that are involved.  Stress leads to disease and the next thing you know is you have sick fish.  Another possibility is diet.  If the fish is not eating enough or afraid to come out and eat then he/she may change color.  Food is an essential part of the daily life of fish and one of their biggest concerns.  Make sure the shark is eating.  I would recommend brine shrimp.  If you have an aggression issue extra food may help to reduce the aggressive nature of most fish including sharks.  Mating is yet one more possibility for color change.  As fish get closer to spawning they may lose color or change color to blend in with their environment better.  This is so that they can spawn or give birth without being in danger from predators.  If the shark is not doing better by tomorrow let me know as it could be sick.  But before you medicate please observe the shark for any of the above issues... please keep me posted... dave