Butterfly the galunggong by cutting the dorsal side of the fish from head to tail.
Remove the entrails and gills of the fish. Then remove also the fish bones. Wash and drain and put in a colander to dry.
In a large container that can fit all the fishes, combine the marinade ingredients: pineapple juice, sugar, garlic, ginger, soy sauce, salt and food coloring.
Mix the marinade ingredients until the sugar is dissolved. Then put the galunggong one by one and rub the marinade on the fishes until well coated.
Cover the container and let it cure overnight in the refrigerator.
To cook the galunggong tocino, heat 1/2 cup of oil in the frying pan and fry the fish until cooked. Serve with fried egg and rice and some sliced tomatoes.