Preheat broiler. Sprinkle fish with ½ tsp chili powder, cumin, ½ lime juice, and salt.
Add aluminum foil to baking sheet. Add fish on top of foil. Put in broiler, placed on the top rack, and cook until fish flakes. For fresh, it should take about 4-6 minutes, for frozen about 8-10 minutes. Add tortilla shells to another baking sheet and add to lower rack in the oven until heated.
While fish is cooking, make chili-lime sauce. Add remaining ½ tsp chili powder, garlic powder, and remaining ½ lime juice. Stir sauce together and let sit a few minutes.
Remove tortilla shells from oven and wrap in a towel to keep warm. When fish appears flakey, remove from oven as well and break apart with a fork.
Add fish, chili-lime sauce, shredded lettuce or coleslaw, avocado, salsa, & cotija cheese to taco shells. Enjoy!