Marinate scallops in lemon juice with salt.
Place trimmed snails in a bowl and cover them with boiling water. Cover and wait until liquid cools (to obtain soft snails). Chop coarsely.
Rinse the octopus and rub with coarse salt. Arrange a layer of thick sliced tomato on the bottom of the saucepan. Place the octopus on top and cooked covered for approximately 25 minutes. It is necessary to test frequently the tenderness of the octopus. If the octopus is not fully cooked or if it is overcooked it will have a hard rubbery consistency.
Remove the octopus from the saucepan and rub it with paper towels or a kitchen cloth to get rid some of the dark skin. Rinse immediately. Cut the head off and discard or reserve it for another preparation. Cut the tentacles in pieces.
Trim squid and cut bodies crosswise into ¼ inch rings. Rinse and cook them in a skillet with boiling water for 1 or 2 minutes. Cook shrimp tails in the same way as the squid.
Once all seafood is ready place them in a glass or ceramic bowl (not aluminum). Season with aji, salt and add onion, leaving some for decoration. Mix well. Place ice cubes on the seafood, pour lime juice and mix. Remove the ice cubes and season to taste.
Serve and garnish with lettuce leaves, sweet potatoes, corn cooked into thick slices, remaining onion and aji limo.