Instructions
Inspect the oscar's vent, or sexual organ. This is located on the underside of the fish beneath the anus. The female vent will be somewhat rounded, while the male vent will have a pointed appearance.
Wait for egg laying. Female oscars will lay eggs even if a male is not present. Oscar eggs are whitish and oval-shaped. If the fish has not laid any eggs, it is most likely a male.
Monitor the other oscar if there are two Oscars present and one is laying eggs. If the other fish is male, his sexual organ will protrude from beneath him during egg laying. The male sexual organ has a thorn-like appearance.
Ask a fish breeder. Many breeders of oscars will have the males and females separated so customers can choose a breeding pair.
How Do I Tell If My Oscar Fish Is Male or Female?
Oscar fish are part of the cichlid family, which is made up of more than 1,000 species and is one of the most popular types fish families for home aquariums. A larger cichlid, it is recommended that an oscar be confined to his or her own tank, since they can sometimes become aggressive. Sexing, or determining if the Oscar is male or female, can be difficult with this species because oscars are monomorphic; meaning both male and female look the same. An oscar's sex cannot be determined by color or markings. Rather, the owner usually has to complete a more thorough inspection of the fish that may take place over a period of time.