1. There are many black fish, such as snakehead, longan fish, black Mary, black koi fish, devil swordfish and so on.

2. Among these fish, snakehead belongs to edible fish, and its scientific name is snakehead, which is an economic fish.

3. Longan stone is a kind of goldfish. It is not only black all over, but also has big eyes, which are very beautiful.

4. Black Mary is a small tropical fish with certain aggressiveness, while black koi fish is a big fish, which requires high dissolved oxygen in water.