General tips
Bag each seafood separately. Clams need 130°F to open, shrimp wants 125°F to stay snappy, and white fish flakes apart at 130°F+. Mixed in one bag, they all cook badly. Use four bags, four temperatures, then combine in the broth at the end.
Build the tomato broth before any seafood goes in the bath. Sauté fennel, garlic, and onions, deglaze with white wine, add crushed tomatoes and clam juice, simmer 30 min. The broth is the heart of cioppino and it can't come together in a bag.
Cook the seafood while the broth simmers. Sous vide the clams first (they take the longest), then the mussels, then the shrimp, then the firm white fish. Each comes out perfectly cooked and you combine them in the warm broth for serving.
Don't boil the broth once seafood is added. Cioppino is a stew, not a boil. Keep the broth at a bare simmer when you add the cooked seafood - just hot enough to warm everything through without overcooking the proteins you carefully sous vide.
Anti-tip: don't skip the sourdough. Cioppino is a San Francisco dish, and sourdough is half the experience. A thick slice toasted and rubbed with garlic, sitting at the bottom of the bowl soaking up broth, is mandatory. No bread, no cioppino.
Tender Seafood tips
Use freshest seafood available
Cook different seafood separately for perfect doneness
Crusty bread is essential for soaking up broth