Krill of Siluridae? Betta bighead.

The picture below shows China fork-tailed fighting fish Macropodus opercularis, commonly known as Paradise Fish, Bodhisattva Fish, Flower Towel, Pond Poor Fish, Black Car Pool, Guanyin Fish, Tangpo Shark and Shigong Fish.

There is a black stripe from the back of the head eye to the gill cover, and there is a dark green circular spot on the gill cover. Adult fish are about 5 to 7 centimeters long. Usually, the male fish is larger, the female fish is smaller, and the male fish is more colorful, with more obvious stripes and more gorgeous colors. The female fish is lighter in color. In addition, the tail fin of male fish will be long and dovetail-shaped, while the tail fin of female fish is short and the dovetail-shaped is not obvious. Male fish can live for 3 to 6 years, and female fish can live for 2 to 3 years.