Be sure to serve this ceviche immediately after mixing in the fruit: fresh mango and pineapple have enzymes that will break down the fish and make it mushy if left for too long.
Pour lime juice and orange juice through a sieve set over a large glass bowl. Add red snapper fillet and gently stir to combine (fish should be completely covered by juice). Cover with plastic wrap and refrigerate until fish is opaque throughout, about 4 hours. Drain fish well; discard marinade. Return fish to bowl.
Add mango, pineapple, tomatoes, chile, red onion, cilantro, and olive oil. Season to taste with salt and pepper and more lime juice, if desired. Serve with tortilla chips.
Fresh fish is key to ceviche; ask for the best at your fish market.