Heat the oil in a pan and fry the garlic until golden. Add the fenugreek seeds and fry for a minute. Then add the onions and fry until golden. Add tomatoes, chili powder, and coriander powder and mix well. Cook for 3-4 minutes. Pour in 1 1/2 cups of water and bring it to a boil. Now add the fish, curry leaves and salt and cook for 15 minutes under medium heat until the fish is cooked. Stir in the yogurt gently and cook for 3 more minutes. Remove from heat and serve hot.