As wattage rates do vary from one microwave to another
, there are a large scale of differing heats available and therefore the speeds at which your fish cooks is going to differ quite significantly depending on which unit you own so I'll work with the average 600-800Watt microwave for my time guide. Microwave on the high setting and I suggest that you cook for a total of 4-5 minutes. Once this time has elapsed and that familiar beeping occurs, pop the door slightly open and let your dish stand for a further 2-3 minutes allowing it to final cook. To check doneness, ideally use a cooking thermometer and aim for 140-145 degrees Fahrenheit, or simply check with a fork making sure that the flesh is just starting to flake. If not, pop it back in for a further minute and let it stand again for another minute before serving.