Heat coconut oil in a pan.
Splutter fenugreek seeds followed by mustard seeds.
Add ginger, garlic and small onion and saute well.
Reduce the flame.
Add turmeric powder, chilly powder coriander powder and salt and fry it lightly.
Add tomato and saute, till it blends.
Add the thick tamarind water and mix well.
Add curry leaves.
Reduce the flame.
Add coconut milk and allow it to boil.
Add very little water as reqd.
When the gravy boils, add fish and cook, till done.