Buy fish only in specialty stores and definitely in the fry rearing age, as then you will be able to determine whether or not they are of the maturity period, after which (especially during spawning) to distinguish males from females is easy.
Sexual maturity of blue and red neons reach the age of 5-9 months, and black – 9-11 months.
Males are blue neons are rarely longer than 3 cm, but females can grow to 4-H. the female is the larger in all parameters, especially in the area of the abdomen. In addition, bright blue-green band on the upper part of the body of this subspecies the females have a few bent males, she video.
In red neon blue-green stripe is much narrower and are located along the body of fish, and the abdomen red. The adult size up to 5 cm, However, females have a rounded abdomen, and the stripe is crooked. The surest way to distinguish the female of the red neon from the male to pay attention to the shape of the anal fin. In the female this fin is concave, the male, on the contrary, convex, rounded.
Strip along the body of fish is a distinctive feature and black neons. Exactly the same as blue and red, the females of the black neon can be distinguished from males by bending the strips (in this case silver). Length of Mature individuals – not more than 4 cm, however, during the spawning season the females increase in size, but males are not.
One of the surest signs to determine the sex of fish is the shape of the swim bladder and how it is located in the abdominal cavity. Consider the fish in bright transmitted light. If individuals bubble pointed shape and goes down, then it is a male. If the bubble is more rounded, and the free space between the rear edge of the abdominal cavity and viscera filled with caviar, then this is definitely a female. But don't get carried away in a similar way to determine the sex of the neons, as they are usually required shaded aquarium.