Substituted 2 seeded and minced jalapenos for the serrano chiles, 1 lb shrimp and 1 lb bay scallops rather than 2 lbs of shrimp, and 1 1/2 large limes, 1 1/2 large lemons, and 1/2 cup of fresh squeezed orange juice rather than the number of limes, lemons and oranges suggested in this shrimp ceviche recipe . After cooking the shrimp and scallops, I ran them under ice water, then marinated them in the citrus juices for 20 minutes, then added all the other ingredients except the avocado. The mixture was chilled in the fridge for several hours until it was ready to serve, then the chopped avocado was added just before serving.
Quite happy with the result, although I might use either more jalapenos or a serrano chile next time. This recipe makes a lot of ceviche. I would probably make a half recipe in the future.