Large freshwater fish
Many of us often mistakenly believe that bigger fish are more delicious and nutritious, so we are willing to spend money to buy these fish to eat. But few people know that most freshwater fish are not very large in size, weighing only about 1.5-2kg after many years of breeding and caring. However, there are also larger fish weighing from 4-7kg that are sold.
You should not buy these types of fish because they may be injected with growth hormones or have been living for a long time in muddy areas, thus accumulating high levels of pollutants. Especially, to achieve such a large size, the fish farmers must have fed the fish with growth-stimulating substances for a long time. Therefore, if you eat these types of fish thinking that they are nutritious, you are only exposing yourself to dangerous toxins.

Swollen fish bellies
When we go to the market, we often like to eat fatty fish or fish with swollen bellies indicating that they have eggs. But in reality, not all fish with swollen bellies are plump with eggs. On the contrary, many fish with swollen bellies may have died a long time ago, and their internal organs may be damaged, resulting in the formation of gas that makes the fish bellies swell. According to nutrition experts, when a fish dies, the immune system weakens and free bacteria thrive. The process of fish decomposition produces organic acids that cause a foul smell and change the color of the fish. The dam histidine content in these fish is extremely toxic to health. Therefore, you should stay away from these types of fish.
Ocean tuna
According to experts, ocean tuna is a type of fish that contains high levels of heavy metals such as lead and mercury. According to the list of health experts, this type of fish is among those that have high levels of mercury. Although tuna is popular, you should avoid eating it to limit the risk of mercury poisoning. Therefore, you should limit eating tuna, lest you invite serious illnesses.

In addition, there are other types of fish that contain high levels of heavy metals, so you should limit eating them:
Mudfish
Mudfish is a dangerous fish for everyone. When consumed, not only does it contain mercury, but it also causes fatal poisoning. Therefore, you should not eat mudfish. Especially, mudfish contains the toxic substances tetradotoxin in the ovaries and hepatoxin in the liver, which are very dangerous. These toxins can poison the body and be life-threatening if not properly processed.

Snakehead fish