The moonfish has a small dorsal fin. Marys have large dorsal fins.

The Mary fish is slightly larger than the moonfish.

Maryfish commonly come in yellow Mary, white Mary, black Mary, and red Mary, all solid colors. There is also a spherical variant of the Mary Fish, the Leatherball Fish. White leatherball, black leatherball, yellow leatherball, and red leatherball, all solid colors as well.

Moonfish come in a lot of colors, with the common ones being the Golden Peony, Tricolor Peony, Mickey, Red Moonlight, and Panda Fish, all of which are usually flowers.

The moonfish and the marlin are close relatives, both are flower killifish. They can be crossed to produce colorful hybrid minnows.

Also, there are swordtails and peacockfish which are also killifish. Most of these 4 species of killifish can interbreed with each other. So sometimes it's not so clear, you have me and I have you. The fish bosses can't tell the difference either.

Swordtails have long slender tail fins (like a sword) and are the largest. There are commonly red swords and red and white swords.

Peacockfish are very, very numerous. Usually the males have nice big tails that look like peacocks opening their screens.

Flower killifish are all very good. They are all fetal fish. Will directly give birth to baby fish. Compared to other fish, you can easily experience the prosperity of raising more and more killifish, and the harvest is full, giving you a sense of satisfaction and achievement. Of course, killifish are also very beautiful.