The dark-edged splitfin (Girardinichthys multiradiatus) is a species of fish in the family Goodeidae endemic to Mexico.

If water is too hot, females will birth their first brood of only 1–3 fry and then die shortly thereafter, which makes it very difficult to maintain a colony.

The species is commonly called the "golden sailfin goodeid" due to their extended fins, especially the males.

The water in which they habitat are mainly considered small lakes, spring-fed ponds, and pools off of colder temperature streams.

[4] The dark-edged splitfin prefers bodies of water that range in clear to muddy visibility, and have a bottom of silt, mud, clay, sand, gravel, and rocks.

They also prefer water depths to be less than 1 m. The habitat of the dark-edged splitfin also includes a variety of green algae.

A study found that much of the contents in the stomach composed of chironomid-larvae, mayflies, Hymenoptera, Diptera-larvae, Detritus, and Cladocera.

[10] The male dark-edged splitfin will then stop the static posture and performs a courtship to attract the female.

[5] Threats to the populations of G. multiradiatus include pollution from urban, industrial, agricultural, and livestock waste.

[5] Lastly, the competition of food between the non-native species and Girardinichthys multiradiatus is a major threat.

[5] There are conservation efforts for the dark-edged splitfin by The Lakes of Zempoala, which is a National Park, and the University of Michoacan.