Heat a large non stick pan on medium heat, when hot, add the fennel, onion, and garlic. Stir often, and cook 4-6 minutes or until the onion is soft. Place mixture into your slow cooker.
To the slow cooker, add 1 bottle of beer, tomato puree, clam juice, bay leaf, salt and pepper as desired. Cover and set to Low setting for 6-8 hours or High setting 3 to 4 hours.
During the last 30 minutes of cooking, place the last bottle of beer and water in a large saucepan, place a steamer basket in the saucepan but keep the basket about the liquid level. Bring to a boil.
To the steamer basket, add the fish, mussels, clams, and shrimp. Cover and steam for 4 to 8 minutes. Discard any mussels or clams that did not open.
Remove the bay leaf from the broth and ladle into serving bowls, place fish, mussels, clams, and shrimp in each bowl. Squeeze lemon juice over the top.
Garnish with parsley, serve, and enjoy.