Add coriander-cumin powder, black pepper powder, turmeric powder, mustard powder, chili powder, amchoor powder and 1/4 cup water then saute the masala for 5 minutes or till masala gets fried very well.. Add 2 cups of water, and bring it to boil. Once it starts boiling, add grilled fish into the curry. Cook it for 2-3 minutes. Turn off the heat. Adjust the consistency of curry as per your taste.