Mollies are popular aquarium fish, interesting and unpretentious pets. The most common species for aquarists are Mollienesia sphenops and Mollienesia velifera. If you decide to start breeding mollies, you need to purchase a male and a female, and for this you need to be able to distinguish between their sex.
Instructions
Step 1
Contrary to popular belief, the sex of mollies can be determined not by the shape of the tail, but by the anal fin. This fin is located on the ventral side of the fish, closest to the caudal fin, near the anus. In female mollies, the anal fin has a triangular shape, while in males it is modified into a copulatory organ called gonopodia, and has the shape of a tube. The female mollies can only spread and fold her fin, while the male can move it in all directions. This sign will help you determine the sex of all viviparous fish (which include mollies).
Step 2
When choosing fry, remember that newly born fish of both sexes have an extended anal fin. Therefore, do not rush to purchase, wait a few weeks.
Step 3
Compare the sizes of males and females. In Mollienesia sphenops, females are significantly larger than males and reach twelve centimeters in length, while males rarely exceed eight centimeters. Moreover, a small and nimble fish will be a stronger and more successful producer. In Mollienesia velifera, on the other hand, the male is larger than the female.
Step 4
If you buy adult fish, then the male Mollienesia velifera can be easily distinguished by the huge dorsal fin, thanks to which this type of mollies got its name "sailing". It usually grows back by one and a half years. In females of this species, the dorsal fin is of the usual size.
