Crush the stalk of lemongrass with the flat side of a cleaver, then cut it into small pieces. Clean the fish and with a sharp knife slash diagonally across the body of the fish. Mix lemongrass, curry powder, salt and peppers. Put the redfish in the mixture, coat well, cover and refrigerate for one hour. Heat oil in a large skillet, and lightly saute the garlic. Then place the redfish in the skillet, let brown very well before turning it over. (If the fish is not very brown it will fall apart.) Brown well on other side, and serrve.