Light fish. According to the Encyclopedia of Fish, traffic lights can be said to be a classic representative species of the Lepidoptera family, with a slim figure. The upper part of the fish is green, which will reflect blue fluorescence in dark environment, while the hip to caudal fin of the fish is bright red, which is in sharp contrast with green. Lampetratidae mainly refers to small tropical fish in CYPRINIDAE and some families of CYPRINIDAE.