How to Tell the Gender of a GloFish

Geneticists use DNA manipulation to add coral DNA to zebrafish make the fish glow a fluorescent green or orange. These modified fish, called GloFish, are widely available to hobbyists. The sex of normal, unmodified, zebrafish is easily established by coloration -- females have silver stripes and males have gold stripes -- but genetically modified fish are often identical in color. Short of dissection, the easiest way to sex a glow fish is to compare it to one of the opposite sex.

Instructions

1. Examine the Cloaca

   • 1

     View your GloFish from the side. You need at least one female and one male for comparison.

   • 2

     Look at the cloaca behind the ventral fin at the rear of the fish. The ventral fin is the last one on the bottom of the fish before the tail. The cloaca is the opening for excretory and sexual functions.

   • 3

     Compare the cloaca to those of other GloFish. It is noticeably larger on female glow fish.