Why do arowana have drop eye?

Question

my arowana have drop eye at left eye, is that permanent?

Answer 1

Arowana typically get droop eye when kept in tanks from an improper diet and from being in a tank too small.  An improper diet is a diet of foods which do not stay on the surface.  Usually this is an indicator the fish keeper is trying to get their Arowana to eat feeder fish, which is not a normal part of it's diet.  In a natural setting, Arowana eat insects and as they age, even smaller rodents and mammals.  

Feeder fish if given have too high of protein in them, and the extra protein causes overdevelopment of the eye muscles, which leaves the eyes looking downward.  This, in addtion with feeder fish seeking cover and not staying on the surface, causes the Arowana to start looking down in a tank.  Once this sets in, it's irreversible short of surgery.