To prepare the couscous: In a medium heatproof bowl, combine couscous with 3/4 cup boiling water, lemon zest and juice. Cover and let stand about 5 minutes or until liquid is absorbed, fluffing with fork occasionally.
Heat 2 teaspoons oil in a small skillet; cook onion and garlic, stirring, until onion softens. Stir onion mixture, nuts and mint through couscous and season to taste.
To prepare the fish: Combine flour, coriander, cumin, paprika and cayenne pepper in medium bowl. Add fish and rub spice mixture all over it.
Heat 1 tablespoon oil in large skillet; cook fish in batches until browned and cooked as desired. Serve with couscous and wedges of lemon.