Are you trying to fry pieces of the fish? I would suggest you to fry the whole fish at one go. Fry in very hot oil and for not more than 2 minutes.
First merinate the fish with some lemon juice salt and turmeric then mix suji salt red chilli powder and turmeric together coat fish with Ainu mixture and shallow. Fry. Or u can marinate the fish with green paste of ginger garlic coriander green chilli and fresh coconut. Then coat it with the sooji mixture and fry
You have to place some weight over the fish for about an hour. So that the water in the fish drains off. After that fry the fish coating it with semolina and serve immediately. If you keep the fried fish for long time it will get soggy