Process coriander, cumin, fennel, ginger, and turmeric with 1/2 cup coconut milk to a paste. Heat oil in pan and pry paste over low heat until an aroma arises. Add balance of coconut milk, tamarind paste, brown sugar, lime juice, salt and jalapeno. Bring mixture to a boil. Add fish and simmer covered for 15 minutes. Serve with rice.