1 pound (450 g) fresh white fish fillets (such as sea bass, sole, or mahi-mahi), diced into 1/2-inch cubes
1 cup fresh lime juice (from about 6-8 limes)
1/2 cup fresh lemon juice (from about 2-3 lemons)
1/4 cup fish stock
1 small red onion, thinly sliced
1 clove garlic, minced
1-inch piece fresh ginger, peeled and minced
1 small celery stalk, finely chopped
1 small habanero or ají amarillo pepper, seeded and finely chopped
1/4 cup fresh cilantro stems, chopped
Salt, to taste
Freshly ground black pepper, to taste
Ice cubes (optional, to chill the mixture)