How to Tell the Sex of Glofish

By Paul Lin

As part of the Zebra fish family, the Glofish awes fish lovers with its genetically modified vibrant, fluorescent colors. Because of its fluorescent nature, observing the physical properties of Glofish requires an illuminated area and clean fish tank. Whether you are attempting to breed your Glofish or are just curious, you can tell the sex of your Glofish with a few physical traits associated with each gender.

Place your aquarium in a lit room and clean your fish tank. Glofish have physical traits that are best seen in water that is clean and a tank that is well illuminated by natural or fluorescent lighting.

Observe the stripe color of the Glofish. Although each Glofish has a blue stripe running across the side of the body, each fish has a secondary color that determines the sex. Under the luminance of a light, if the Glofish has golden stripes, the sex is a male. If the secondary line is silver, the sex is a female.

Determine the physical size and shape of the Glofish. Females tend to be larger than male Glofish and are more round in appearance. Males are more petite and slender in width.