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.