My answer would be gambooge / kodumpuli ..it imparts a smoky and tangy flavor to the fish and the gravy.Fish is cooked in an earthenware which makes all the difference one is sure to notice.
Let me tell you how I make:
4.Heat oil put ginger when raw smell goes add onion and saute it till it is transparent then add green chili, turmeric pd,kashmiri chili pd,coriander pd when powders turn slightly brownish add kudampuli (with the water it is soaked in)and 2 cups of water.let it boil.
6.Pour the coconut paste,fenugreek powder swirl the dish till everything is well combined and remove from flame.Do not mix with spoon as fish tends to crumble.
I haven't used garlic in this dish.
I have used two types of chili pd so one gives heat and other is for color .Make it as much hot as you want .
You can use the canned coconut milk instead of fresh .
Think of me when you prepare this curry:) and let me know what you think.
Nadan konju theeyal / Chemmeen theeyal / Shrimp in coconut and tamarind sauce