How to Tell If a Neon Tetra Is a Male or Female?

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The neon tetra is a popular tropical freshwater aquarium fish. This colorful little fish is hardy and readily available. Commonly called 'neons,' the inexpensive neon tetra is popular with both novice and advance aquarists. This social species always adds both color and movement to an aquarium.

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The neon tetra is a popular tropical freshwater aquarium fish.
Image Credit: cejoos/iStock/GettyImages

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The neon tetra is small and peaceful and therefore suitable for the majority of community aquariums — however, might be eaten by larger species. These small fish are not immediately easy to sex, but with practice, an aquarist can learn to identify neon tetra male and female behavior. How they interact with each other is the best way to determine gender. Stripes are a clue too.

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Tetra spawning environment

Keep a small school of neon tetras together. Neon tetras are not always easy to sex, but by watching the fish interact with each other, you will find it easier to sex them correctly. Replace half of the aquarium water with fresh water, because this will induce the neon tetras to begin spawning.

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Feed live food, such as mosquito larvae and brine shrimp, at this time. Live food will also encourage the fish to begin spawning. Observe the fish during the early morning, because this is typically the time they begin to spawn.

Neon tetra spawning behavior

To determine a neon tetra male vs female, observe the spawning behavior carefully. Look out for the fish that is performing a dance around another. The fish which is actively displaying short jerky movements is a male. This fish will also chase the female through the aquatic plants in the aquarium.

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Turn on the aquarium light so that you can see the tetras clearly. Look closely at the fish. Those individuals with rounded bellies are female. This full-bodied look is caused by the eggs that have developed within the female. Male neon tetras are slimmer.

Neon tetra male and female appearance

Observe the horizontal blue stripe that runs along the flank of the fish. This line is straight in male fish and bends slightly in the females. It is the rounded flanks of the female that causes this color stripe to bend, but the phenomenon assists the aquarist to sex this species of fish.

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Also look for egg lying. Clearly, the fish which is laying is female. Once she had deposited her eggs onto aquatic plants and other décor in the tank, the male swims over the eggs and deposits his milt or sperm over them.

Black neon tetra male vs female

Black neon tetras originate from the tropical freshwater of southern Brazil. These tiny fish are dark with a greenish hue, with one white stripe that glows under light and a second black stripe. Black neon tetras become stressed when lonely, exposed to too much bright light, or poor water conditions. Their color will start to fade.

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Sex the black tetra exactly in the same manner as you have sexed the standard neon tetra. Females are slightly longer and, like neon tetras, have rounder bellies. However, both male and female black tetras will darken in color during the breeding period, so you can not use this characteristic to tell male fish apart from female fish.

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