Cut halibut into bite-size pieces. Place in a mixing bowl and combine with soy sauce and 1 tablespoon of flour. Let stand for 30 minutes.
Meanwhile, heat oil in deep-fryer or heavy saucepan and deep fry the halibut pieces until golden brown. Drain on paper towels; set aside.
For the Sauce, saute green capsicum, onion and pineapple in a medium frypan for 1 minute. Stir in reserved pineapple juice, tomato sauce, water, remaining 2 teaspoons of flour, sesame oil, and salt to taste. Cook until thickened, stirring occasionally.
Serve, by dipping fried halibut pieces into sauce, or pour the sauce over the fish.