In the meantime, soak the mussels in lightly salted water for 10 minutes. Then brush under cold water and remove the beards. Throw away damaged copies or opened copies that do not close when you tap them lightly. Put the rest in a saucepan with a little water, bring to the boil and cook over high heat for 4 minutes until they open. Remove from heat and remove unopened mussels.
As soon as the tomato mixture is ready, rinse the fish fillets, pat dry and cut into pieces. Pour into the saucepan and simmer for 5 minutes. Add the mussels, prawns and scallops and season with salt and pepper. Cook for 3 minutes until the fish is cooked through. Remove from heat, remove the bay leaf, pour the bouillabaisse into soup bowls and serve.