This comrade is really interesting. How do you know what fish it is without putting the picture? I guess it is a kind of crucian carp. It is called engineering crucian carp, Yunxiang crucian carp. It is a hybrid of crucian carp and carp. It is much bigger than ordinary crucian carp, weighing three or four kilograms. Easy to grow up, strong resistance. You can search the internet to see if I'm right. I'm not sure.