1. Sautee onion, tomatoes, carrots, celery, garlic, bell peppers, tomato sauce, salt and pepper in a saucepan. Set aside.
2. Boil 4 liters of water, add fish head and shrimp bouillon.
3. Add sautéed vegetables, let boil for a couple of minutes, then add in crab legs, octopus, calamari, mussels, and shrimp.
4. Add catfish pieces last and let boil until fish is cooked through.
5. Serve soup with onion, cilantro, lime, chile de arbol peppers, and tortillas or tostadas.