Heat a frying pan over a medium heat and add one tablespoon of the olive oil. Add half of the sliced garlic and cook for one minute, without browning. Add the chopped tomatoes, stir and cook for ten minutes, or until the volume of liquid has reduced slightly. Set aside.
Heat two lidded sauté pans over a medium heat and add one tablespoon of the olive oil to each pan. Divide the remaining sliced garlic equally between the two pans. Fry the garlic for one minute, without browning. Add the clams to one pan and the mussels to the other, then cover both pans with a lid. (Cooking the mussels and clams beforehand and straining the liquid will prevent any grit from the shellfish making its way into the finished dish.)
Cook the mussels and clams for two minutes, then add half of the white wine to each pan and cover again with the lids. Cook for for an additional four minutes, or until all the clams and mussels have opened (discard any shellfish that remain closed).
Strain the mussels and clams, discarding the liquid from the cooked clams but retaining the liquid from the cooked mussels. Set aside the mussels and clams, in their shells.
Heat the reserved liquid from the cooked mussels in a small saucepan until the volume of liquid has reduced by half.
Once the mussels and clams are cool enough to handle, remove the meat from the shells and set aside.
In a large frying pan heat the remaining tablespoon of olive oil over a high heat. Add the sea bass and squid slices and cook for two minutes (the squid should colour slightly).
Add the cooked mussels and clams, the strained juice from cooking the mussels, the brown shrimps, chopped parsley and chilli flakes, then season, to taste, with salt and freshly ground black pepper. Reduce the heat and stir in the tomato sauce until warmed through.
Meanwhile, bring a large pan of salted water to the boil. Add the taglierini and cook for 2-3 minutes, or until al dente.
Drain the pasta and add it to the sauce in the pan. Toss well to combine and add more freshly ground black pepper, to taste. Divide equally among four serving plates.