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 to 375 degrees F (190 degrees C).
Deep fry halibut pieces until golden brown. Drain on paper towels; set aside.
For the Sauce, saute green pepper, onion and pineapple in a medium skillet for 1 minute. Stir in reserved pineapple juice, sugar, ketchup, 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.