Note: It isn't that much trouble to make a double batch of the sauce, and it keeps forever in the freezer. ~ 2 cups/serving so ~4 cups for dinner for two. Real convenient for the next time you start Jonesin' for cioppino. One other thing, save all those shells after a crab feast. Or even shrimp feast. Or lobster. Use them to make a batch of stock. Shellfish stock is the bomb, and turns cioppino from merely excellent to absolutely magical.
R&D: large fennel bulb sliced thin, 3 large shallots chopped, ¼ cup tomato paste (drop puree, total 5 cups stock), 1 ½ cups dry white wine. Test some heat