Cut the fillets into bite-size pieces. Cut the shrimp in half lengthwise. Place in a shallow, nonreactive bowl and set aside.
Combine the tomatoes, onion, cilantro, garlic, chile, lime juice, oil, salt and pepper in a food processor fitted with the metal blade. Process until smooth. Pour over fish and allow to marinate for 1 hour.
Place marinated fish in a heavy saucepan over medium heat. Add the bell peppers and fish stock. Bring to a boil. Lower heat and simmer for about 10 minutes or until fish is cooked through. Serve immediately with rice, if desired.