Pre-cook the brown rice in a separate pot. If you use white rice (I never do) you could cook it in the broth before adding the fish.Saute the onion and garlic with a pinch of salt in a heavy bottomed stock pot until the onion is translucent (about 12 minutes).Add the marjoram and mint, tomato paste and tomatoes. Bring to a simmer.Add the fish stock and water and pepper. Bring back to a simmer.Add the fish and cook until done, about 5 - 10 minutes.Break up the fish into small pieces with a wooden spoon. Some traditional recipes run the whole soup through a sieve, but I prefer it a bit more rustic and chunky.Add the rice and stir.Serve hot, stirring in about a tablespoon of fresh lemon juice. Garnish with a lemon wedge.