1. Cook pasta according to package directions, omitting salt and fat; drain.
2. While pasta cooks, heat 1 tablespoon oil in a large nonstick skillet over medium-high heat. Add scallops and shrimp to pan; cook 3 minutes. Remove scallop mixture from pan; keep warm. Heat remaining 1 tablespoon oil in pan over medium-high heat. Add onion, red pepper, and garlic; cook 2 minutes. Add tomato paste and tomatoes; bring to a boil, and cook 2 minutes. Add clam juice; cook 1 minute. Add clams; cover, reduce heat to medium, and cook 4 minutes. Add mussels; cover and cook 3 minutes or until clams and mussels open. Discard any unopened shells. Stir in scallop mixture and parsley; cook 1 minute or until thoroughly heated. Serve over pasta. Sprinkle with basil.