Defrost the prawns if necessary. Wash and sort the mussels and remove the beard (see recipe: mussels in white wine stock). Rinse fish fillet, dab dry and cut into cubes. Wash shrimps and pat dry.
Peel and finely dice the onion and garlic. Heat 2 tablespoons of oil in a large pot. Fry the onion and garlic in it. Add the tomatoes and juice and chop a little. 3⁄4 Add l water. Season with salt, pepper, sugar and 1 tsp. chili flakes, bring to the boil.
Add the noodles and simmer for about 5 minutes. Add mussels to the noodles, bring to the boil again and simmer covered for about 8 minutes, stirring from time to time.
In the meantime heat 2 tablespoons of oil in a large frying pan. Fry the prawns for approx. 3 minutes, turning them over and taking them out. Fry the fish in the hot frying fat all around for about 4 minutes. Season with salt and pepper.
Wash basil, shake dry, cut leaves into strips. Season pasta to taste again, remove closed mussels. Carefully fold prawns and fish into the noodles. Serve sprinkled with basil.