In a large pot drizzle some olive oil and add the 2 garlic cloves, peeled and halved. Add all the cleaned mussels and clams, making sure to throw away the cracked ones as they may have sand inside.
Turn on the heat to medium and cover the pot with the lid to steam the mussels and clams. Stir a couple of times and once they are all open, turn off the heat and set aside.
In another large pan, drizzle some more olive oil, add the 2 finely chopped shallots, the tomato paste and the rinsed rice. Turn on the heat to medium and toast the rice for a couple of minutes, until traslucent (be careful not to burn the shallot).
Pour the white wine and let it evaporate completely, then add the fish stock a couple of ladles at a time until completely absorbed. Cook for about 20 minutes, adding more liquid when necessary.
Halfway through the cooking time of the rice, add the mussels' water instead of the stock (if it's becoming too salty, add plain water). Add the cleaned and deveined shrimps and the cleaned squids, cut in rings.
When the rice is done, turn off the heat and add the mussels, clams, the finely chopped parsley and the chili pepper flakes before serving.