Clean all the fish, keeping the discards aside, and cut them into coarse pieces. Wash the mussels under running water, remove the byssus and brush the outside with a straw. Cook them in a pan with a little oil and a lid until they open.
Pour 2 liters of water into a pot, add 1 onion, 2 stalks of celery, half a glass of white wine and the discarded fish and let simmer for about an hour. Once ready, filter the broth and keep it aside.
Chop the onion, garlic and chili pepper and sauté in a large saucepan with a little olive oil. Pour the squid and cuttlefish and cook for 5 minutes, blend with half a glass of white wine, add the peeled tomatoes and season with salt and pepper. Pour in some fish broth and cook over a low heat with a lid for about 30 minutes.
When the fish is almost cooked add the monkfish, redfish and shrimp and continue cooking for another 10-15 minutes by adding broth if necessary. At the end add the shelled mussels.