Season fish. Dredge in flour and fry until golden brown. Place in serving dish. Set aside.
Saute garlic and ginger in oil. Add onions, pepper, carrots and celery. Continue to stir fry. Add vinegar, pineapple juice, sugar and tomato sauce. Continue to simmer for 5 minutes. Season to taste. Add cornstarch, pineapple and tomatoes. Cook until it thickens. Pour on top of fish in serving dish. Garnish with green onions.