Place the diced fish in a bowl and cover with lime and lemon juice. Make sure the fish is fully submerged in the juice. Cover and refrigerate for about 2 hours, or until the fish is opaque and fully "cooked" by the citrus juice.
In a separate bowl, mix the chopped onion, tomatoes, cucumber, bell pepper, and minced garlic.
After the fish has marinated, drain off some of the citrus juice, leaving a small amount to coat the fish. Add the prepared vegetables to the fish. Mix well.
Chill in the refrigerator for an additional 15 minutes before serving. Serve the ceviche with tortilla chips, plantain chips, or on its own.
Enjoy your meal!