1Combine rice and water in a medium saucepan. Bring to a simmer over medium heat; cover and cook until the water is absorbed, about 20 minutes. Stir in lemon zest and juice.
2Meanwhile, bring broth to a simmer in another medium saucepan over medium-high heat. Reduce the heat so the broth remains steaming, but not simmering. Add fish and cook until just tender, about 5 minutes. Remove and break into bite-size chunks.
3Divide the lemony rice among 4 bowls. Top with equal portions of the fish, arugula (or watercress), carrot, mint and scallions. Ladle 1 cup of the warm broth into each bowl and serve.
Tip: Look for U.S. farm-raised tilapia, which is usually grown in closed farming systems that limit pollution and prevent escapes. Some Central and South American tilapia is farmed in this manner as well, but avoid tilapia from China and Taiwan, mostly farmed in open systems.