In medium bowl, combine the potato flakes, flour, garlic powder, seasoning salt, black pepper, and cayenne pepper.
Soak fish filets in bowl of cold water.
In a deep skillet or deep fryer, melt and heat the shortening to 350 degrees F (175 degrees C).
Dredge fish filets in dry mixture and fry in the hot oil for 5 minutes or until fish flakes apart easily. Remove from oil and place on paper towels to absorb excess oil.