1, maybe you accidentally broke your guts while killing fish.
2. The other is that you didn't remove the black film on the inner wall of the fish head cavity, so you feel a little bitter.
3. I suggest that the next time you cook fish head soup, first heat the pot, add some oil, stir-fry the onion and ginger, then fry both sides of the fish head, add hot water or warm water, add some old wine or cooking wine after boiling, then simmer for a while, and just add some coriander when eating.