Rinse the rice and place in a bowl. Pour in three cups of water. Soak for at least six hours in the fridge.
Rinse the mussels. Place in a bowl, cover with water and soak in the fridge until the shells open a bit.
Rinse the shrimps, cut off the tentacles and place in a bowl. Cover with water and keep in the fridge until needed.
Rinse the salmon fillet and pat dry with paper towels. Cut into two-inch cubes. Sprinkle with salt and pepper. Keep in a covered container in the fridge.
Drain the rice.
Drain the mussels and pull off the beards.
Boil one and a half cups of water. Drop the mussels into the boiling water. When the water boils again, scoop out the mussels and cool.
Strain the mussel broth to remove grits.
Heat the olive oil and butter in a wide shallow pan. Saute the onion, tomatoes, bell peppers and garlic with the turmeric and paprika.
Pour in the broth. Season with patis and pepper.
Stir the rice into the broth. When the broth boils, cover the pan, lower the heat and let the rice cook for about 10 minutes.
Meanwhile, discard the empty half shells of the mussels.
Spread the shrimps, mussels, salmon and peas over the rice. Cover the pan and cook for another 10 minutes.
Drizzle the lemon juice over the cooked seafood arroz a la Valenciana. Sprinkle with chopped mint, parsley or scallions. Serve at once.