Heat the oil in a very large pot over medium heat. Add the celery and onion, scallions and sea salt and sauté until the onion is translucent, about 10 minutes. Add the garlic and 1/4 teaspoon of red pepper flakes, and sauté 2 minutes. Add tomatoes with their juices, potatoes, wine, fish stock and bay leaf. Cover and bring to a simmer. Reduce the heat to medium-low. Cover and simmer until the flavors blend, about 30 minutes.
Add the clams and mussels to the cooking liquid. Cover and cook until the clams and mussels begin to open, about 5 minutes. Add the fish. Simmer gently until the fish is just cooked through, and the clams are completely open, stirring gently, about 5 minutes longer (discard any clams and mussels that do not open). Season the soup, to taste, add shrimp last & simmer about 3 minutes, until shrimp are cooked through & still tender. Taste & add more seasoning if necessary. Stir. Turn off heat.
Ladle the soup into bowls and serve with large loaf of crusty Italian Bread (Or over your favorite pasta)! YUMMMMO!