11 ounces red snapper portions, skin off, sliced into ¼-inch slices
22 ounces fluke fillets, sliced into ¼-inch slices
6 lemons, juiced
1 grapefruit, wedged (without membrane); keep the juice
1 small red onion, cut into short, thin strips
3 serrano chiles, minced (including seeds and membrane)
1 cucumber, peeled, halved lengthwise, seeded, and diced
1 nectarine or peeled mango, cored, and cut into small cubes
1 avocado, halved, pitted, sliced, and scooped out with a spoon
1 bunch cilantro leaves, minced
1 bunch parsley leaves, minced
kosher salt, to taste