When did you last change the water?
Water quality is the utmost impotant thing when you keep fish in a tank/bowl. After all you do not keep fish, you keep water quality.
You should change the water every other day if the fish is in a bowl, due to the ammonia build up after they have done their pooing an weeeing.
When you add water from the tap you should add a de-chlorinator to the water so that the water is safe for the fish. Contact your local fishkeeping shop for further advice.