Defrost the mussels and crab tails. Cut the fish fillet into portion pieces. Peel and dice the garlic cloves and onions.
Clean, rinse, seed and dice the peppers. Blanch (scald) the tomatoes, remove the skin, remove the seeds and cut into cubes.
Preheat the oven to 180 °C together with a large gratin dish.
Heat 4 tbsp oil in a frying pan. Add the diced choritzo and roast for 5 min, then season with salt, bell pepper and paprika. Add the garlic cubes, onion cubes, bell bell pepper cubes and tomato cubes and sauté for another 5 min. Then remove the quantity from the frying pan and set aside.
Heat new oil in the frying pan. Add the long grain rice and sauté briefly, then add the hot fish stock (in which the saffron was boiled).
Pour the long grain rice and the clear soup into the preheated gratin dish and spread evenly. Add the vegetable-sausage mixture and fold it in, then add the fish pieces, the mussels and the crab tails and press them a little into the broth.
Put the gratin dish in the oven. Cook the dish for about 25 minutes until the long grain rice is soft. Alternatively, it can also be cooked in a frying pan on the stove at low temperature.
When the liquid is absorbed by the rice, season with salt and freshly ground pepper, garnish with lemon quarters and serve on the spot.