These days eating vegetarian and non vegetarian is a problem. The reason being that both are grown and stored in unhygienic and unscientific conditions. While the vegetables are grown in murky conditions and sewer water is being used, the fish is stored in chemicals to keep them fresh.
Like the ripening of mangoes with chemicals, the fish is stored in chemical so that it stays hard and looks fresh for consumption. Most of the hotels are storing them in unhygienic conditions and they are brought in containers with chemical waters. It is reported that this is causing cancer.
If the fish is caught in regular flowing water it is a good one. If it is brought from commercial tanks it is not that good. But if they are used after storage for a long time then you are in trouble. If the same fish is stored in chemical and used for consumption it causes health hazards and would finally lead to cancer.
It is the same with fruits and vegetables. Apples are coated with wax to keep them fresh and increase the shelf life. They are bad for health. Most of the star hospitals give you this wax coated apples. It is the same with 5-star hotels also.
If the apple shines and glitters then you have to wash it with hot water to remove the wax coating. Wash the fish and other Non-vegetarian thoroughly to remove the chemicals from them. It is the same with vegetables also. Washing and boiling them is very much essential.