Combine the rice with 1 3/4 cups water and the sliced ginger in a medium saucepan; season with salt and pepper. Bring to a boil, cover and reduce the heat to low. Cook until the water is absorbed and the rice is tender, about 16 minutes. Remove from the heat and let sit, covered, 5 minutes.
Meanwhile, heat 2 tablespoons vegetable oil in a large skillet over medium-high heat. Add the thyme, bell peppers, onion and 1/4 teaspoon salt; cook, stirring, until softened, 5 to 6 minutes. Add the remaining 1 tablespoon vegetable oil, the garlic and grated ginger and cook, stirring, until the garlic is golden, about 1 minute. Stir in the curry powder and cook until toasted, about 30 seconds. Add the tomatoes, 1/2 cup water and 1/2 teaspoon salt and bring to a boil. Cover and cook, stirring occasionally, until saucy, 6 to 7 minutes.
Season the fish with salt and pepper. Reduce the heat to low and nestle the fish in the sauce. Cover and cook, turning the fish halfway through, until just cooked through, 6 to 8 minutes.
Discard the ginger from the rice and divide the rice among bowls. Top with the fish and discard the thyme. Top with cilantro and serve with lime wedges.