We predominantly cook fish curries in 2 ways..this is my favorite way which goes well with some fishes like pomfret, kane(ladyfish) and even prawns.

Method
1. Wash 7-8 Kane fish(also called Lady fish) thoroughly, apply a little salt and set aside.
2.  Take a small pan, add  1 tsp coconut oil and when hot, add 1 -2 tsp coriander seeds, pinch of fenugreek seeds and 5-6 whole dry red chillies. Saute lightly for 2 mins
3. Grind them with 1 cup of grated coconut,  pinch of turmeric powder and 1 inch ball of tamarind to a fine paste. 
4. Take a bigger pan. Heat 2 tsp coconut oil and add 1 onion finely chopped and saute till pink.Add a pinch of fenugreek seeds, 2 green chillies slit at the centre and saute. You can use any other oil, but coconut oil gives it a distinct Konkani flavor.
5. Add the coconut paste and fry for 2-3 mins. Add 2-3 cups of water and let the mixture come to a good boil. I also add 2-3 Dried Sol for added sourness. 
6. Now add the fish and let the curry come to a good boil. Adjust the salt according to taste. This fish cooks within 5 mins. 
7. Serve hot with plain rice.