Combine 2 1/2 cups water and bottled clam juice in medium saucepan. Bring to simmer and keep warm over low heat.
Heat 3 Tbl olive oil in heavy large saucepan over medium heat. Add shallots and mushrooms; saute until shallots are light golden, about 4 minutes. Add rice; saute 2 minutes. Add wine; stir until liquid is absorbed, about 2 minutes. Add stewed tomatoes; cook until liquid is absorbed, about 3 minutes.
Add 1 cup clam juice mixture to rice. Simmer until liquid is absorbed, stirring often. Continue adding clam juice mixture by 1/2 cupfuls until rice is tender, but still slightly firm in center and mixture is creamy, simmering until liquid is absorbed before each addition and stirring often, about 25 minutes.
Heat bacon in heavy large skillet over medium high heat until fat is rendered (should be about 3 Tbl fat) and bacon is slightly brown. Add shrimp, scallops and garlic and saute until shrimp and scallops are opaque in center, about 6 minutes. Mix seafood into rice. Cook 3 minutes longer. Season with salt and pepper and stir in gremolata just before serving. (Seafood can be sauted while rice is absorbing liquid).
3 or 4 garlic cloves, chopped.
bunch of chopped flat leaf parsley.
grated zest of 2 lemons.
(this makes more than the 2 Tbl you need but it keeps relatively well and can be used in other dishes.).