You can use any fleshy fish to make this recipe.
Do a taste test of tamarind to see it's strength and add accordingly. Also some tamarind may be too salty, in that case, be careful while adding salt to the curry.
Make sure you give enough resting time for the dish, since the flavour develops as it rests. Also, you can adjust the qty of gravy to suit your requirements. keep in mind that gravy tends to reduce as it rests.