Defrost frozen seafood. Clean the mussels and wash them thoroughly under cold running water. Wash squid tubes, shrimps and fish fillets and pat dry. Cut squid into rings and fish into pieces.
Clean, wash and chop the peppers. Peel and chop onion and garlic.
Heat 2 tablespoons of oil in a large (paella) frying pan. Fry the fish, squid and prawns over medium heat for 3-5 minutes while turning. Season with salt and pepper. Remove everything from the pan.
Heat 2 tablespoons of oil in a frying pan. Sauté the bell pepper, onion and garlic. Add rice and steam briefly. Mix 1 l hot water with saffron and 1⁄2 tsp. salt, pour on and bring to the boil.
Add the mussels and simmer together, stirring frequently, for about 20 minutes until all the liquid is absorbed. Add frozen peas, fried fish and seafood, and cook for the last 5 minutes.
Finally, cover the paella with a tea towel and let it rest for 5-8 minutes. Sort out closed mussels. Season paella with salt, pepper and lemon juice