In a large pot, heat half of the olive oil and gently brown three cloves of garlic, the sage, and the chili pepper. Add the seafood, starting with the octopus, cuttlefish, and squid, and cook briefly to develop flavor. Add the dogfish, and after a few minutes, pour in the red wine along with the tomato paste diluted in a splash of water. Simmer and cook for about 30 minutes.
In a separate, smaller pot, heat the remaining olive oil and sauté the chopped celery and one clove of garlic. Add the cod, the peeled, seeded, and chopped tomatoes, and a splash of water. Let simmer gently for approximately 20 minutes.
Pour the contents of the smaller pot into the large pot. When the cephalopods are tender and nearly cooked through, add the prawns and langoustines. Cook for an additional 2 to 3 minutes, then remove from heat.
Toast the slices of Tuscan bread and rub them with the remaining raw garlic clove. Arrange the bread around the rim of a large serving dish and ladle the cacciucco into the center, or divide the toasted bread and stew among six individual serving bowls.
