Begin by preparing the fish (ihanda ang isda). Bring water to a boil (100°C/212°F) in a large pot (kaldero). Add the tanigue and sliced ginger (luya), boiling for 10 minutes or until the fish reaches an internal temperature of 63°C/145°F. Remove fish and let cool completely.
Once cooled, remove the skin and bones from the fish and flake the meat into bite-sized pieces. Season with vinegar (suka), salt (asin), pepper (paminta), and half of the chopped garlic (bawang). Let marinate for 5 minutes.
Heat a medium saucepan (kawali) over medium heat (175°C/350°F). Add the coconut milk (kakang gata) and sliced onions (sibuyas). Stir continuously for 3 minutes until onions soften. It's crucial to stir gently to prevent the coconut milk from curdling.
Drain the marinated fish and add it to the coconut milk mixture. Simmer until the liquid reduces by 25%, about 10 minutes. Add the moringa leaves (malunggay), green finger chilies (siling pangsigang), red bird's eye chilies (siling labuyo), and remaining garlic. Cook until the sauce thickens, about 5-7 minutes, or until it reaches 74°C/165°F.
Serve hot with steaming white rice (kanin) and calamansi halves on the side. For best results, let the dish rest for 5 minutes before serving to allow flavors to meld together.